A367060 G.f. satisfies A(x) = 1 + x*A(x)^3 + x^3*A(x)^4.

1, 1, 3, 13, 62, 318, 1718, 9627, 55437, 326070, 1950630, 11831706, 72597453, 449804148, 2810260317, 17685019893, 111997074910, 713223954540, 4564502770117, 29341499243806, 189364923816282, 1226535071582818, 7970416067268898, 51949175133236526

Offset: 0

Author

Seiichi Manyama, Nov 04 2023

Keywords

• nonn

Crossrefs

Cf. A366676, A367057, A367058, A367059, A367061, A367062.

Programs

PARI

a(n) = sum(k=0, n\3, binomial(2*n-2*k+1, k)*binomial(3*n-5*k, n-3*k)/(2*n-2*k+1));

Formula

a(n) = Sum_{k=0..floor(n/3)} binomial(2*n-2*k+1,k) * binomial(3*n-5*k,n-3*k)/(2*n-2*k+1).