A371778 a(n) = Sum_{k=0..floor(n/3)} binomial(3*n+2,n-3*k).

1, 5, 28, 166, 1015, 6324, 39901, 254035, 1628380, 10493680, 67914088, 441086947, 2873255906, 18763759019, 122803467241, 805241108334, 5288922607095, 34789875710568, 229147231044397, 1511104857207706, 9975701630282920, 65920216186587257

Offset: 0

Author

Seiichi Manyama, Apr 05 2024

Keywords

• nonn

Crossrefs

Cf. A371777, A371779, A371780.

Cf. A066380.

Programs

PARI

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

Formula

a(n) = [x^n] 1/(((1-x)^3-x^3) * (1-x)^(2*n)).