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A223711
Number of n X 2 0..1 arrays with row sums and column sums unimodal.
2
4, 16, 53, 155, 418, 1066, 2611, 6205, 14408, 32852, 73825, 163951, 360574, 786574, 1704095, 3670193, 7864516, 16777432, 35651821, 75497731, 159383834, 335544626, 704643403, 1476395365, 3087008128, 6442451356, 13421773241, 27917287895
OFFSET
1,1
COMMENTS
Column 2 of A223716.
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) - 19*a(n-2) + 25*a(n-3) - 16*a(n-4) + 4*a(n-5).
Conjectures from Colin Barker, Mar 16 2018: (Start)
G.f.: x*(2 - 3*x + 2*x^2)^2 / ((1 - x)^3*(1 - 2*x)^2).
a(n) = (-2*(2^(3+n)-9) + (5+2^(3+n))*n + n^2) / 2.
(End)
EXAMPLE
Some solutions for n=3:
..1..0....0..0....1..1....0..0....1..0....0..1....1..0....0..0....0..0....0..0
..0..1....1..0....1..0....0..1....1..1....0..1....0..1....0..1....1..1....1..0
..1..0....1..0....0..1....1..0....0..0....0..0....0..0....1..1....1..0....0..0
CROSSREFS
Cf. A223716.
Sequence in context: A375307 A220936 A232399 * A074409 A056589 A074407
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 26 2013
STATUS
approved