A383538 a(n) = Sum_{k=0..floor(n/4)} binomial(n+k,k)^2 * binomial(n-3*k,k).

1, 1, 1, 1, 26, 73, 148, 257, 2431, 9676, 26984, 61993, 332762, 1487886, 5029676, 13986049, 57394823, 253491517, 953613991, 3032424076, 11249004334, 47032861778, 185321607072, 645015386921, 2340940921276, 9321743657318, 37091865274327, 136525692171310

Offset: 0

Author

Seiichi Manyama, Apr 29 2025

Keywords

• nonn

Comments

Diagonal of the rational function 1 / ((1-x)*(1-y)*(1-z) - z^4).

Crossrefs

Cf. A383536, A383537.

Programs

PARI

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