A366364 G.f. satisfies A(x) = (1 + x/A(x)^2)/(1 - x).

1, 2, -2, 14, -70, 426, -2714, 18118, -124814, 881042, -6339058, 46318334, -342769750, 2563781690, -19350683018, 147197511222, -1127334112542, 8685458120226, -67270210217186, 523472089991662, -4090668558473318, 32088204418069450, -252576222775705466

Offset: 0

Author

Seiichi Manyama, Oct 08 2023

Keywords

• sign

Crossrefs

Cf. A346626, A349310, A349311, A349312, A349313, A349314, A366363, A366365, A366366.

Cf. A366357.

Programs

PARI

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

Formula

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