OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
J. Brzozowski, M. Szykula, Large Aperiodic Semigroups, arXiv:1401.0157 [cs.FL], 2013 (Tables 1, 2).
FORMULA
a(n) = A002003(n) + n.
Conjecture: n*(n-3)*a(n) -4*(2*n-1)*(n-3)*a(n-1) +2*(7*n^2-28*n+20)*a(n-2) -4*(n-1)*(2*n-7)*a(n-3) +(n-1)*(n-4)*a(n-4)=0. - R. J. Mathar, Feb 01 2014
Recurrence: (n-2)*n*(2*n^2 - 8*n + 7)*a(n) = (14*n^4 - 88*n^3 + 189*n^2 - 158*n + 39)*a(n-1) - (14*n^4 - 80*n^3 + 153*n^2 - 112*n + 24)*a(n-2) + (n-3)*(n-1)*(2*n^2 - 4*n + 1)*a(n-3). - Vaclav Kotesovec, Feb 14 2014
a(n) ~ 2^(-3/4) * (3+2*sqrt(2))^n / sqrt(Pi*n). - Vaclav Kotesovec, Feb 14 2014
MATHEMATICA
Table[2*Sum[Binomial[n-1, k]*Binomial[n+k, k], {k, 0, n-1}]+n, {n, 0, 20}] (* Vaclav Kotesovec, Feb 14 2014 *)
Flatten[{0, Table[n+2*Hypergeometric2F1[1-n, 1+n, 1, -1], {n, 1, 20}]}] (* Vaclav Kotesovec, Feb 14 2014 *)
PROG
(PARI) for(n=0, 25, print1(n + 2*sum(k=0, n-1, binomial(n-1, k) * binomial(n+k, k)), ", ")) \\ G. C. Greubel, Jun 01 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 31 2014
STATUS
approved