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Array T(m,n) read by antidiagonals: number of domino tilings (or dimer tilings) of the m X n grid (or m X n rectangle), for m>=1, n>=1.
+10
52
0, 1, 1, 0, 2, 0, 1, 3, 3, 1, 0, 5, 0, 5, 0, 1, 8, 11, 11, 8, 1, 0, 13, 0, 36, 0, 13, 0, 1, 21, 41, 95, 95, 41, 21, 1, 0, 34, 0, 281, 0, 281, 0, 34, 0, 1, 55, 153, 781, 1183, 1183, 781, 153, 55, 1, 0, 89, 0, 2245, 0, 6728, 0, 2245, 0, 89, 0, 1, 144, 571, 6336, 14824, 31529, 31529, 14824, 6336, 571, 144, 1
OFFSET
1,5
COMMENTS
There are many versions of this array (or triangle) in the OEIS. This is the main entry, which ideally collects together all the references to the literature and to other versions in the OEIS. But see A004003 for further information. - N. J. A. Sloane, Mar 14 2015
REFERENCES
S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 406-412.
P. E. John, H. Sachs, and H. Zernitz, Problem 5. Domino covers in square chessboards, Zastosowania Matematyki (Applicationes Mathematicae) XIX 3-4 (1987), 635-641.
R. P. Stanley, Enumerative Combinatorics, Vol. 1, Cambridge University Press, 2nd ed., pp. 547 and 570.
Darko Veljan, Kombinatorika: s teorijom grafova (Croatian) (Combinatorics with Graph Theory) mentions the value 12988816 = 2^4*901^2 for the 8 X 8 case on page 4.
LINKS
M. Aanjaneya and S. P. Pal, Faultfree tromino tilings of rectangles, arXiv:math/0610925 [math.CO], 2006.
Mudit Aggarwal and Samrith Ram, Generating Functions for Straight Polyomino Tilings of Narrow Rectangles, J. Int. Seq., Vol. 26 (2023), Article 23.1.4.
F. Ardila and R. P. Stanley, Tilings, arXiv:math/0501170 [math.CO], 2005.
M. Ciucu, Enumeration of perfect matchings in graphs with reflective symmetry, Journal of Combinatorial Theory, Series A, Volume 77, Issue 1, January 1997, Pages 67-97.
Henry Cohn, 2-adic behavior of numbers of domino tilings, arXiv:math/0008222 [math.CO], 2000.
Henry Cohn, 2-adic behavior of numbers of domino tilings, Electronic Journal of Combinatorics, 6 (1999), #R14.
Steven R. Finch, The Dimer Problem [From Steven Finch, Apr 20 2019]
Steven R. Finch, Two Dimensional Monomer Dimer Constant [Broken link]
M. E. Fisher, Statistical mechanics of dimers on a plane lattice, Physical Review, 124 (1961), 1664-1672.
P. Flajolet and R. Sedgewick, Analytic Combinatorics, 2009; see page 363.
Laura Florescu, Daniela Morar, David Perkinson, Nicholas Salter, and Tianyuan Xu, Sandpiles and Dominos, Electronic Journal of Combinatorics, Volume 22(1), 2015.
W. Jockusch, Perfect matchings and perfect squares J. Combin. Theory Ser. A 67 (1994), no. 1, 100-115.
Peter E. John and Horst Sachs, On a strange observation in the theory of the dimer problem, arXiv:math/9801094 [math.CO], 1998.
Peter E. John and Horst Sachs, On a strange observation in the theory of the dimer problem, Discrete Math. 216 (2000), no. 1-3, 211-219.
Yuhi Kamio, Junnosuke Koizumi, and Toshihiko Nakazawa, Quadratic residues and domino tilings, arXiv:2311.13597 [math.NT], 2023.
David Klarner and Jordan Pollack, Domino tilings of rectangles with fixed width, Disc. Math. 32 (1980) 45-52, Table 1.
Douglas M. McKenna, The Art of Space-Filling Domino Curves, Bridges Conference Proceedings, 2024, pp. 319-326.
J. Propp, Enumeration of Matchings: Problems and Progress, arXiv:math/9904150v2 [math.CO], 1999.
Jaime Rangel-Mondragon, Polyominoes and Related Families, The Mathematica Journal, 9:3 (2005), 609-640.
R. C. Read, A Note on Tiling Rectangles with Dominoes, The Fibonacci Quarterly, 18.1 (1980), 24-27.
H. N. V. Temperley and Michael E. Fisher, Dimer problem in statistical mechanics -- an exact result, Philos. Mag. (8) 6 (1961), 1061-1063.
Herman Tulleken, Polyominoes 2.2: How they fit together, (2019).
Eric Weisstein's World of Mathematics, Domino Tiling
Eric Weisstein, Illustration for T(4,4) = 36, from Domino Tilings web page (see previous link) [Included with permission]
FORMULA
T(m, n) = Product_{j=1..ceiling(m/2)} Product_{k=1..ceiling(n/2)} (4*cos(j*Pi/(m+1))^2 + 4*cos(k*Pi/(n+1))^2).
EXAMPLE
0, 1, 0, 1, 0, 1, ...
1, 2, 3, 5, 8, 13, ...
0, 3, 0, 11, 0, 41, ...
1, 5, 11, 36, 95, 281, ...
0, 8, 0, 95, 0, 1183, ...
1, 13, 41, 281, 1183, 6728, ...
MAPLE
(Maple code for the even-numbered rows from N. J. A. Sloane, Mar 15 2015. This is not totally satisfactory since it uses floating point. However, it is useful for getting the initial values quickly.)
Digits:=100;
p:=evalf(Pi);
z:=proc(h, d) global p; evalf(cos( h*p/(2*d+1) )); end;
T:=proc(m, n) global z; round(mul( mul( 4*z(h, m)^2+4*z(k, n)^2, k=1..n), h=1..m)); end;
[seq(T(1, n), n=0..10)]; # A001519
[seq(T(2, n), n=0..10)]; # A188899
[seq(T(3, n), n=0..10)]; # A256044
[seq(T(n, n), n=0..10)]; # A004003
MATHEMATICA
T[_?OddQ, _?OddQ] = 0;
T[m_, n_] := Product[2*(2+Cos[2j*Pi/(m+1)]+Cos[2k*Pi/(n+1)]), {k, 1, n/2}, {j, 1, m/2}];
Flatten[Table[Round[T[m-n+1, n]], {m, 1, 12}, {n, 1, m}]] (* Jean-François Alcover, Nov 25 2011, updated May 28 2022 *)
PROG
(PARI) {T(n, k) = sqrtint(abs(polresultant(polchebyshev(n, 2, x/2), polchebyshev(k, 2, I*x/2))))} \\ Seiichi Manyama, Apr 13 2020
CROSSREFS
See A187596 for another version (with m >= 0, n >= 0). See A187616 for a triangular version. See also A187617, A187618.
See also A004003 for more literature on the dimer problem.
Main diagonal is A004003.
KEYWORD
tabl,nonn
AUTHOR
Ralf Stephan, Oct 16 2004
EXTENSIONS
Old link fixed and new link added by Frans J. Faase, Feb 04 2009
Entry edited by N. J. A. Sloane, Mar 15 2015
STATUS
approved
Number of domino tilings of 4 X (n-1) board.
(Formerly M3813)
+10
27
0, 1, 1, 5, 11, 36, 95, 281, 781, 2245, 6336, 18061, 51205, 145601, 413351, 1174500, 3335651, 9475901, 26915305, 76455961, 217172736, 616891945, 1752296281, 4977472781, 14138673395, 40161441636, 114079985111, 324048393905
OFFSET
0,4
COMMENTS
Or, number of perfect matchings in graph P_4 X P_{n-1}.
a(0) = 0, a(1) = 1 by convention.
It is easy to see that the g.f. for indecomposable tilings, i.e., those that cannot be split vertically into smaller tilings, is g = x + 4x^2 + 2x^3 + 3x^4 + 2x^5 + 3x^6 + 2x^7 + 3x^8 + ... = x + 4x^2 + x^3*(2+3x)/(1-x^2); then g.f. = 1/(1-g) = (1-x^2)/(1-x-5x^2-x^3+x^4). - Emeric Deutsch, Oct 16 2006
This is a divisibility sequence; that is, if n divides m, then a(n) divides a(m). - T. D. Noe, Dec 22 2008
From Artur Jasinski, Dec 20 2008: (Start)
All numbers in this sequence are:
congruent to 0 mod 100 if n is congruent to 14 or 29 mod 30
congruent to 1 mod 100 if n is congruent to 0 or 1 or 12 or 16 or 27 or 28 mod 30
congruent to 5 mod 100 if n is congruent to 2 or 11 or 17 or 26 mod 30
congruent to 11 mod 100 if n is congruent to 3 or 25 mod 30
congruent to 36 mod 100 if n is congruent to 4 or 9 or 19 or 24 mod 30
congruent to 45 mod 100 if n is congruent to 8 or 20 mod 30
congruent to 51 mod 100 if n is congruent to 13 or 15 mod 30
congruent to 61 mod 100 if n is congruent to 10 or 18 mod 30
congruent to 81 mod 100 if n is congruent to 6 or 7 or 21 or 22 mod 30
congruent to 95 mod 100 if n is congruent to 5 or 23 mod 30
(End)
This is the case P1 = 1, P2 = -7, Q = 1 of the 3 parameter family of 4th-order linear divisibility sequences found by Williams and Guy. - Peter Bala, Mar 31 2014
REFERENCES
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. P. Stanley, Enumerative Combinatorics I, p. 292.
LINKS
Steve Butler, Jason Ekstrand, Steven Osborne, Counting Tilings by Taking Walks in a Graph, A Project-Based Guide to Undergraduate Research in Mathematics, Birkhäuser, Cham (2020), see page 158.
Curtis Cooper and Robert E. Kennedy, Problem B-735: Soln 1, Problem B-735: Soln 2, Square Root of a Recurrence, The Fibonacci Quarterly, 32(2):185-186, May 1994, and 32(4):374-375, Aug 1994.
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.
Vladimir Victorovich Kruchinin, Composition of ordinary generating functions, arXiv:1009.2565 [math.CO], 2010.
R. J. Mathar, Paving Rectangular Regions with Rectangular Tiles: Tatami and Non-Tatami Tilings, arXiv:1311.6135 [math.CO], 2013, Table 3.
Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992
Simone Rinaldi and D. G. Rogers, Indecomposability: polyominoes and polyomino tilings, The Mathematical Gazette 92.524 (2008): 193-204.
David Singmaster, Letter to N. J. A. Sloane, Oct 3 1982.
Thotsaporn ”Aek” Thanatipanonda, Statistics of Domino Tilings on a Rectangular Board, Fibonacci Quart. 57 (2019), no. 5, 145-153. See p. 151.
Herman Tulleken, Polyominoes 2.2: How they fit together, (2019).
H. C Williams, R. K. Guy, Some fourth-order linear divisibility sequences, Intl. J. Number Theory 7 (5) (2011) 1255-1277
H. C. Williams and R. K. Guy, Some Monoapparitic Fourth Order Linear Divisibility Sequences Integers, Volume 12A (2012) The John Selfridge Memorial Volume.
Li Zhou, Northwestern University Math Problem Solving Group, Christopher Carl Heckman and Jerry Minkus, Tiling 4-Rowed Rectangles with Dominoes: 11187, The American Mathematical Monthly 114 (2007): 554-556.
FORMULA
a(n) = a(n-1) + 5*a(n-2) + a(n-3) - a(n-4).
G.f.: x*(1 - x^2)/(1 - x - 5*x^2 - x^3 + x^4).
Limit_{n->infinity} a(n)/a(n-1) = (1 + sqrt(29) + sqrt(14 + 2*sqrt(29)))/4 = 2.84053619409... - Philippe Deléham, Jun 12 2005
a(n) = (5*sqrt(29)/145)*(((1+sqrt(29)+sqrt(14+2*sqrt(29)))/4)^n+((1+sqrt(29)-sqrt(14+2*sqrt(29)))/4)^n-((1-sqrt(29)+sqrt(14-2*sqrt(29)))/4)^n-((1-sqrt(29)-sqrt(14-2*sqrt(29)))/4)^n). - Tim Monahan, Jul 30 2011
From Peter Bala, Mar 31 2014: (Start)
a(n) = ( T(n,alpha) - T(n,beta) )/(alpha - beta), where alpha = (1 + sqrt(29))/4 and beta = (1 - sqrt(29))/4 and T(n,x) denotes the Chebyshev polynomial of the first kind.
a(n) = the bottom left entry of the 2 X 2 matrix T(n, M), where M is the 2 X 2 matrix [0, 7/4; 1, 1/2].
a(n) = U(n-1,i*(1 + sqrt(5))/4)*U(n-1,i*(1 - sqrt(5))/4), where U(n,x) denotes the Chebyshev polynomial of the second kind.
See the remarks in A100047 for the general connection between Chebyshev polynomials and 4th-order linear divisibility sequences. (End)
a(n) = A129113(n+2) - A129113(n). - R. J. Mathar, May 03 2021
EXAMPLE
For n=2 the graph is
. o-o-o-o
and there is one perfect tiling:
. o-o o-o
For n=3 the graph is
. o-o-o-o
. | | | |
. o-o-o-o
and there are five perfect tilings:
. o o o o
. | | | |
. o o o o
two like:
. o o o-o
. | | ...
. o o o-o
and this
. o-o o-o
. .......
. o-o o-o
and this
. o o-o o
. | ... |
. o o-o o
a(n+1)=r(n)-r(n-2), r(n)=if n=0 then 1 else sum(sum(binomial(k,j)*sum(binomial(j,i-j)*5^(i-j)*binomial(k-j,n-i-3*(k-j))*(-1)^(n-i-3*(k-j)),i,j,n-k+j),j,0,k),k,1,n), n>1. - Vladimir Kruchinin, Sep 08 2010
MAPLE
a[0]:=1: a[1]:=1: a[2]:=5: a[3]:=11: for n from 4 to 26 do a[n]:=a[n-1]+5*a[n-2]+a[n-3]-a[n-4] od: seq(a[n], n=0..26); # Emeric Deutsch, Oct 16 2006
A005178:=-(-1-4*z-z**2+z**3)/(1-z-5*z**2-z**3+z**4) # conjectured (correctly) by Simon Plouffe in his 1992 dissertation; gives sequence apart from an initial 1
MATHEMATICA
CoefficientList[Series[x(1-x^2)/(1-x-5x^2-x^3+x^4), {x, 0, 30}], x] (* T. D. Noe, Dec 22 2008 *)
LinearRecurrence[{1, 5, 1, -1}, {0, 1, 1, 5}, 28] (* Robert G. Wilson v, Aug 08 2011 *)
a[0] = 0; a[n_] := Product[2(2+Cos[2j Pi/5]+Cos[2k Pi/n]), {k, 1, (n-1)/2}, {j, 1, 2}] // Round;
Table[a[n], {n, 0, 27}] (* Jean-François Alcover, Aug 20 2018 *)
PROG
(Maxima) r(n):=if n=0 then 1 else sum(sum(binomial(k, j)*sum(binomial(j, i-j)*5^(i-j)*binomial(k-j, n-i-3*(k-j))*(-1)^(n-i-3*(k-j)), i, j, n-k+j), j, 0, k), k, 1, n); a(n):=r(n)-r(n-2); /* Vladimir Kruchinin, Sep 08 2010 */
CROSSREFS
Row 4 of array A099390.
For all matchings see A033507.
Cf. A003757. - T. D. Noe, Dec 22 2008
Bisection (odd part) gives A188899. - Alois P. Heinz, Oct 28 2012
Column k=2 of A250662.
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, David Singmaster, Frans J. Faase
EXTENSIONS
Amalgamated with (former) A003692, Dec 30 1995
Name changed and 0 prepended by T. D. Noe, Dec 22 2008
Edited by N. J. A. Sloane, Nov 15 2009
STATUS
approved
Complexity of (or spanning trees in) a 3 X n grid.
(Formerly M4986)
+10
10
1, 15, 192, 2415, 30305, 380160, 4768673, 59817135, 750331584, 9411975375, 118061508289, 1480934568960, 18576479568193, 233018797965135, 2922930580320960, 36664523428884015, 459910778352898337, 5769007865476035840, 72365017995700730081, 907729015392142395375
OFFSET
1,2
COMMENTS
a(n) is a divisibility sequence - m divides n implies that a(m) divides a(n). - Paul Raff, Mar 06 2009
Also number of domino tilings of the 5 X (2n-1) rectangle with upper left corner removed. For n=2 the 15 domino tilings of the 5 X 3 rectangle with upper left corner removed are:
. .___. . .___. . .___. . .___. . .___. . .___. . .___. . .___.
._|___| ._| | | ._|___| ._|___| ._|___| ._| | | ._| | | ._|___|
| |___| | |_|_| | | | | | |___| | |___| | |_|_| | |_|_| | | | |
|_|___| |_|___| |_|_|_| |_| | | |_|___| |_| | | |_|___| |_|_|_|
| |___| | |___| | |___| | |_|_| | | | | | |_|_| | | | | | | | |
|_|___| |_|___| |_|___| |_|___| |_|_|_| |_|___| |_|_|_| |_|_|_|
. .___. . .___. . .___. . .___. . .___. . .___. . .___.
._|___| ._|___| ._|___| ._|___| ._|___| ._|___| ._| | |
|___| | | | | | |___| | |___| | |___| | | |___| | |_|_|
|___|_| |_|_|_| | | |_| |___|_| |___|_| |_|___| |_|___|
|___| | |___| | |_|_| | | | | | | |___| |___| | |___| |
|___|_| |___|_| |___|_| |_|_|_| |_|___| |___|_| |___|_|
- Alois P. Heinz, Apr 14 2011
REFERENCES
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.
Germain Kreweras, Complexité et circuits Eulériens dans les sommes tensorielles de graphes, J. Combin. Theory, B 24 (1978), 202-212.
P. Raff, Spanning Trees in Grid Graphs, arXiv:0809.2551 [math.CO], 2008.
P. Raff, Analysis of the Number of Spanning Trees of P_3 x P_n. Contains sequence, recurrence, generating function, and more.
Hugh Williams, R. K. Guy, Some fourth-order linear divisibility sequences, Intl. J. Number Theory vol. 7 (5) (2011) 1255-1277
FORMULA
a(n) = 15a(n-1) - 32a(n-2) + 15a(n-3) - a(n-4), n>4.
G.f.: -x(x^2-1)/(x^4-15x^3+32x^2-15x+1). - Paul Raff, Mar 06 2009
a(n) = A001906(n)*A004254(n). - R. J. Mathar, Jun 03 2009
From Peter Bala, Mar 25 2014: (Start)
a(n) = ( T(n,alpha) - T(n,beta) )/(alpha - beta), where alpha = (15 + sqrt(105))/4 and beta = (15 - sqrt(105))/4 and T(n,x) denotes the Chebyshev polynomial of the first kind.
a(n) = the bottom left entry of the 2X2 matrix T(n, M), where M is the 2X2 matrix [0, -15/2; 1, 15/2].
See the remarks in A100047 for the general connection between Chebyshev polynomials of the first kind and 4th-order linear divisibility sequences. (End)
a(n) = (A003775(n+1)+A003775(n-2))/24-(A003775(n)+A003775(n-1))/3, n>1. - Sergey Perepechko, Apr 26 2016
MAPLE
a:= n-> (<<0|1|0|0>, <0|0|1|0>, <0|0|0|1>, <-1|15|-32|15>>^n. <<1, 0, 1, 15>>)[2, 1]: seq(a(n), n=1..30); # Alois P. Heinz, Apr 14 2011
MATHEMATICA
LinearRecurrence[{15, -32, 15, -1}, {1, 15, 192, 2415}, 30] (* Harvey P. Dale, May 14 2013 *)
CROSSREFS
Row 3 of A116469. A100047.
KEYWORD
nonn
STATUS
approved
Number of perfect matchings (or domino tilings) in the graph P_9 X P_2n.
+10
6
1, 55, 6336, 817991, 108435745, 14479521761, 1937528668711, 259423766712000, 34741645659770711, 4652799879944138561, 623139489426439754945, 83456125990631342400791, 11177167872295392172767936, 1496943834332592837945956455, 200483802581126644843760725601
OFFSET
0,2
LINKS
J. L. Hock and R. B. McQuistan, A note on the occupational degeneracy for dimers on a saturated two-dimensional lattice space, Discrete Applied Mathematics, 1984, v.8, 101-104.
Per Hakan Lundow, Computation of matching polynomials and the number of 1-factors in polygraphs, Research report, No 12, 1996, Department of Math., Umea University, Sweden.
Index entries for linear recurrences with constant coefficients, signature (209, -11936, 274208, -3112032, 19456019, -70651107, 152325888, -196664896, 152325888, -70651107, 19456019, -3112032, 274208, -11936, 209, -1).
FORMULA
a(n) = 209*a(n-1) - 11936*a(n-2) + 274208*a(n-3) - 3112032*a(n-4) + 19456019*a(n-5) - 70651107*a(n-6) + 152325888*a(n-7) - 196664896*a(n-8) + 152325888*a(n-9) - 70651107*a(n-10) + 19456019*a(n-11) - 3112032*a(n-12) + 274208*a(n-13) - 11936*a(n-14) + 209*a(n-15) - a(n-16). - Jay Anderson (horndude77(AT)gmail.com), Apr 07 2007
G.f.: (1 - 154x + 6777x^2 - 123961x^3 + 1132714x^4 - 5684515x^5 + 16401668x^6 - 27757938x^7 + 27757938*x^8 - 16401668x^9 + 5684515x^10 - 1132714x^11 + 123961x^12 -6777x^13 + 154x^14 - x^15)/(1 - 209x + 11936x^2 - 274208x^3 + 3112032x^4 - 19456019x^5 + 70651107x^6 - 152325888x^7 + 196664896x^8 - 152325888x^9 + 70651107x^10 -19456019x^11 + 3112032x^12 - 274208x^13 + 11936x^14 - 209x^15 + x^16). - Sergey Perepechko, Nov 23 2012
MATHEMATICA
T[_?OddQ, _?OddQ] = 0;
T[m_, n_] := Product[2(2+Cos[2 j Pi/(m+1)]+Cos[2 k Pi/(n+1)]), {k, 1, n/2}, {j, 1, m/2}];
a[n_] := T[2n, 9] // Round;
Table[a[n], {n, 0, 20}] (* Jean-François Alcover, May 28 2022 *)
PROG
(PARI) {a(n) = sqrtint(polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(9, 2, I*x/2)))} \\ Seiichi Manyama, Apr 13 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Edited by N. J. A. Sloane, Jul 03 2008 at the suggestion of R. J. Mathar
STATUS
approved
Number of matchings in graph P_{5} X P_{n}.
+10
4
1, 8, 228, 5096, 120465, 2810694, 65805403, 1539222016, 36012826776, 842518533590, 19711134149599, 461148537211748, 10788744980331535, 252406631116215534, 5905146419664967132, 138153075553825008696
OFFSET
0,2
COMMENTS
These are the row sums of the following triangle of the matchings of P_5 X P_n with k>=0 monomers (A003775 appears in the first column):
1;
0, 3, 0, 4, 0, 1;
8, 0, 56, 0, 94, 0, 56, 0, 13, 0, 1;
0, 106, 0, 757, 0, 1670, 0, 1597, 0, 758, 0, 185, 0, 22, 0, 1;
95, 0, 2111, 0, 12181, 0, 29580, 0, 36771, 0, 25835, 0, 10769, 0, 2696, 0, 395, 0, 31, 0, 1;
0, 2180, 0, 35104, 0, 192672, 0, 510752, 0, 762180, 0, 695848, 0, 407620, 0, 157000, 0, 39979, 0, 6632, 0, 686, 0, 40, 0, 1;
1183, 0, 52614, 0, 611633, 0, 3146447, 0, 8803727, 0, 14957414, 0, 16492039, 0, 12307901, 0, 6380454, 0, 2329148, 0, 600254, 0, 108186, 0, 13295, 0, 1058, 0, 49, 0, 1;
0, 37924, 0, 1054776, 0, 10405842, 0, 51732687, 0, 151233778, 0, 283790459, 0, 361377070, 0, 324069497, 0, 209807278, 0, 99625091, 0, 34985010, 0, 9096697, 0, 1740018, 0, 240905, 0, 23414, 0, 1511, 0, 58, 0, 1;
- R. J. Mathar, May 06 2016
LINKS
F. Cazals, Monomer-Dimer Tilings, 1997.
Per Hakan Lundow, Computation of matching polynomials and the number of 1-factors in polygraphs, Research report, No 12, 1996, Department of Math., Umea University, Sweden.
FORMULA
For g.f. see Maple program. - Sergey Perepechko, Apr 26 2013
MAPLE
# The following g.f. is for the sequence a(0)=1, a(1)=8, a(2)=228, etc.
Gf:= (1-6*x-113*x^2+88*x^3+1794*x^4-1994*x^5-6956*x^6+7532*x^7+
11175*x^8-9448*x^9-9255*x^10+4700*x^11+3820*x^12-870*x^13-654*x^14+
68*x^15+45*x^16-2*x^17-x^18)/(1-14*x-229*x^2+16*x^3+4757*x^4-898*x^5-
35106*x^6+26564*x^7+74665*x^8-60482*x^9-73623*x^10+50158*x^11+
38553*x^12-17604*x^13-10366*x^14+2538*x^15+1281*x^16-140*x^17-65*x^18+
2*x^19+x^20):
expr:=convert(series(Gf, x, 21), polynom):
seq(coeff(expr, x, j), j=0..20);
# Sergey Perepechko, Apr 26 2013
CROSSREFS
Column 5 of triangle A210662.
KEYWORD
nonn
AUTHOR
STATUS
approved
Number of domino tilings of the 5 X n grid with upper left corner removed iff n is odd.
+10
3
1, 1, 8, 15, 95, 192, 1183, 2415, 14824, 30305, 185921, 380160, 2332097, 4768673, 29253160, 59817135, 366944287, 750331584, 4602858719, 9411975375, 57737128904, 118061508289, 724240365697, 1480934568960, 9084693297025, 18576479568193, 113956161827912
OFFSET
0,3
FORMULA
G.f.: (x-1)*(1+x)*(x^4+x^3-6*x^2+x+1) / (-x^8+15*x^6-32*x^4+15*x^2-1).
MAPLE
a:= n-> (<<0|1|0|0>, <0|0|1|0>, <0|0|0|1>, <-1|15|-32|15>>^iquo(n, 2, 'r').
`if`(r=0, <<8, 1, 1, 8>>, <<1, 0, 1, 15>>))[3, 1]:
seq(a(n), n=0..30);
MATHEMATICA
a[n_] := Product[2(2+Cos[2 j Pi/(n+1)]+Cos[k Pi/3]), {k, 1, 2}, {j, 1, n/2} ] // Round;
Table[a[n], {n, 0, 24}] (* Jean-François Alcover, Aug 19 2018, after A099390 *)
CROSSREFS
5th row of array A189006.
Bisections give: A003775 (even part), A006238 (odd part).
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Apr 15 2011
STATUS
approved
The number of vertically fault-free domino tilings of the 5 X (2n) board.
+10
1
1, 8, 31, 175, 1015, 5911, 34447, 200767, 1170151, 6820135, 39750655, 231683791, 1350352087, 7870428727, 45872220271, 267362892895, 1558305137095, 9082467929671, 52936502440927, 308536546715887, 1798282777854391, 10481160120410455, 61088677944608335
OFFSET
0,2
COMMENTS
A003775 counts the tilings of the 5 X (2n) board, and this sequence here counts only those that cannot be broken into tilings of two or more smaller 5 X (2n') boards with edge lengths n' < n by cutting "vertically" through the tiling parallel to the "short" side of length 5.
Technically speaking this is the inverse INVERT transform of A003775 (see the comment in A005178).
FORMULA
G.f.: (1 + x - 18*x^2 + 13*x^3 - x^4)/((1-x)*(1 - 6*x + x^2)).
a(n) = 1 + 6*A001653(n) for n>1. - Bruno Berselli, Nov 27 2013
a(n) = 6*a(n-1) - a(n-2) - 4, n>=4. - R. J. Mathar, Nov 07 2015
a(n) = 1 + (3/2)*(3-2*sqrt(2))^n*(2+sqrt(2)) + (3-3/sqrt(2))*(3+2*sqrt(2))^n for n>1. - Colin Barker, Mar 05 2016
PROG
(PARI) Vec((-18*x^2+13*x^3-x^4+x+1)/((1-x)*(1-6*x+x^2)) + O(x^30)) \\ Colin Barker, Mar 05 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Nov 27 2013
STATUS
approved
Numbers m with m mod 3 = q, q != 2, such that the number of ones in its base-2 representation is even if q=0 and odd if q=1.
+10
1
0, 1, 3, 4, 6, 7, 9, 12, 13, 15, 16, 18, 19, 22, 24, 25, 27, 28, 30, 31, 33, 36, 37, 39, 45, 48, 49, 51, 52, 54, 55, 57, 60, 61, 63, 64, 66, 67, 70, 72, 73, 75, 76, 78, 79, 82, 88, 90, 91, 94, 96, 97, 99, 100, 102, 103, 105, 108, 109, 111, 112, 114, 115, 118, 120, 121
OFFSET
0,3
COMMENTS
For q=0, the terms in A180963 are excluded.
The terms of the sequence occur, with some exceptions, while tiling a wall (odd width w) with 1 X 2 dominos. The current tiling status can be described by a number x with 0 <= x < 2^w. In the base-2 representation, 1 stands for an overstanding unit square, see example.
Statement:
The tiling always starts with q=1 and an odd number of ones (type 1) and is followed by a term with q=0 and an even number of ones (type 2) and so on, alternately.
Proof:
Start, provisionally, with w upright dominos. The corresponding term is x = (11..1) = 2^w-1 with x mod 3 = 1 (type 1). Another first profile can be generated by replacing a pair of adjacent upright dominos with one flat domino. In the base-2 representation, this is the subtraction (11..11..1) - (00..11..0) = (11..00..1). The subtrahend is 3*2^j with 0 <= j < w. Therefore, the modified term also is type 1. This way, any first profile can be found and it is type 1.
In the next provisional step, an upright domino is placed on each not overstanding unit square. If p1 is the first profile, then the second is p2 = 2^w - 1 - p1 with p2 mod 3 = 0. Moreover, the transition from p1 to p2 exchanges the ones and zeros such that p2 is type 2. Again, replacing adjacent upright dominos by one flat domino does not change the type of the profile. The next profile is type 1 and so on. QED. Condition to be satisfied by a tiling profile: The continued removal of 00 and 11 (reduction) leads to (0) or (1). Example: a(10)=18=(10010) -> (110) -> (0). The first exceptions are a(314) = 682 = (01010101010), a(611) = 1365 = (10101010101) and a(988) = 2218 = (0100010101010). Note that the reduction of 2218 is 682.
EXAMPLE
5 X 4 wall is tiled bottom-up with 1 X 2 dominos:
_ ___ ___ _
_ _ _ _ ___| | |_ _|___| |
_ | | |_ ___ | | |_ _|_| | | |_ _|_|
___| |___ |_|_| |___| |_|_| |___| |_|_| |___|
|___|_|___| |___|_|___| |___|_|___| |___|_|___|
0 0 1 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 0 0
4 = a(3) 24 = a(14) 1 = a(1) 0 = a(0)
PROG
(Maxima)
block(kmax: 100, a:[],
even_ones(x):= block(su:0,
while x>0 do(p: mod(x, 2), x:(x-p)/2, su:su+p),
return(mod(su, 2))),
for k from 0 thru kmax do(r:mod(k, 3),
if r<2 and r=even_ones(k) then a:append(a, [k])), a);
(PARI) isok(m) = my(k=m%3); if (hammingweight(m) % 2, k==1, k==0); \\ Michel Marcus, Feb 27 2023
KEYWORD
nonn
AUTHOR
Gerhard Kirchner, Feb 24 2023
STATUS
approved
Numbers Sum_{i=1..2r+1} 2^k(i) such that k(1) is even and, for r > 0 and i < 2r+1, the difference k(i+1)-k(i) is > 0 and odd.
+10
1
1, 4, 7, 16, 19, 25, 28, 31, 64, 67, 73, 76, 79, 97, 100, 103, 112, 115, 121, 124, 127, 256, 259, 265, 268, 271, 289, 292, 295, 304, 307, 313, 316, 319, 385, 388, 391, 400, 403, 409, 412, 415, 448, 451, 457, 460, 463, 481, 484, 487, 496, 499, 505, 508, 511, 1024
OFFSET
1,2
COMMENTS
This is a subsequence of A360799. Another description of the terms: in the base-2 representation, the number of ones is odd and all zeros are grouped in blocks of even length.
That is why the terms less than 2^(2j+1) describe start profiles for tiling a (2j+1) X m wall with 1 X 2 dominos, see examples and A360799.
EXAMPLE
A 5 X m wall is tiled bottom-up with dominos, start profiles:
_ _ _ _ _ _ _ _ _ _ _ _ _
___ ___| | ___| |___ ___| | | | | |___| | | | | | | | |
|___|___|_| |___|_|___| |___|_|_|_| |_|___|_|_| |_|_|_|_|_|
0 0 0 0 1 0 0 1 0 0 0 0 1 1 1 1 0 0 1 1 1 1 1 1 1
1 = a(1) 4 = a(2) 7 = a(3) 19 = a(5) 31 = a(7)
also the mirror images of 1 (16), 19 (25) and 7 (28).
PROG
(Maxima)
block(kmax: 100, a:[],
oddsum(y):= block(su1:0, su2:0, pold:0, ok: true,
while y>0 and ok do(p:mod(y, 2), y:(y-p)/2,
if p=1 then(if pold=0 and su2=1 then ok:false, su1:1-su1, su2:0)
elseif p=0 then su2:1-su2, pold:p), return(is(ok and su1=1))),
for k from 1 thru kmax do if oddsum(k) then a:append(a, [k]), a);
KEYWORD
nonn
AUTHOR
Gerhard Kirchner, Feb 24 2023
STATUS
approved

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