A379025 a(n) = Sum_{k=0..n} binomial(3*n+k-1,k) * binomial(3*n+k,n-k).

1, 6, 78, 1149, 17850, 285711, 4661727, 77086008, 1287322866, 21661521945, 366687839133, 6237631866417, 106535632157643, 1825763898882189, 31379978657609100, 540688387589377764, 9336602657251874754, 161534120354250452361, 2799488717098336992687

Offset

0,2

Links

Table of n, a(n) for n=0..18.

Formula

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

Prog

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

Crossrefs

Cf. A262910, A379022, A379026.

Sequence in context: A197103 A345360 A208473 * A358956 A268555 A131926

Adjacent sequences: A379022 A379023 A379024 * A379026 A379027 A379028

Keyword

nonn,new

Author

Seiichi Manyama, Dec 14 2024

Status

approved