A391407 Expansion of g^4/(1 + x*g)^2, where g = 1+x*g^3 is the g.f. of A001764.

1, 2, 11, 52, 271, 1460, 8107, 46036, 266134, 1561012, 9266929, 55573104, 336162522, 2048697862, 12567146031, 77532920596, 480777987559, 2994852486212, 18731746252378, 117593059787784, 740692678560938, 4679713043486622, 29649222733534441, 188331093974572132

Offset

0,2

Links

Table of n, a(n) for n=0..23.

Formula

G.f.: B(x)^2, where B(x) is the g.f. of A391294.

a(n) = Sum_{k=0..n} (-1)^k * (k+1) * (k+4) * binomial(3*n-2*k+4,n-k)/(3*n-2*k+4).

Prog

(PARI) a(n) = sum(k=0, n, (-1)^k*(k+1)*(k+4)*binomial(3*n-2*k+4, n-k)/(3*n-2*k+4));

Crossrefs

Cf. A374835, A391405.

Cf. A001764, A114495, A391294.

Sequence in context: A110308 A027201 A026933 * A346925 A052171 A333542

Adjacent sequences: A391404 A391405 A391406 * A391408 A391409 A391410

Keyword

nonn

Author

Seiichi Manyama, Dec 08 2025

Status

approved