A370055 a(n) = 3*(3*n+2)!/(2*n+3)!.

1, 3, 24, 330, 6552, 171360, 5581440, 218045520, 9945936000, 519177859200, 30535045632000, 1998518736614400, 144098325316915200, 11350405033583616000, 969837188805041356800, 89351761457237190912000, 8830056426362263572480000, 931769828125956695715840000

Offset

0,2

Links

Table of n, a(n) for n=0..17.

Formula

E.g.f.: exp( Sum_{k>=1} binomial(3*k,k) * x^k/k ).

a(n) = 3*A076151(n+1) for n > 0.

a(n) = A000142(n)*A001764(n+1). - Alois P. Heinz, Feb 08 2024

Prog

(PARI) a(n) = 3*(3*n+2)!/(2*n+3)!;

Crossrefs

Cf. A001763, A370054.

Cf. A065866, A370058.

Cf. A076151.

Cf. A000142, A001764.

Sequence in context: A319939 A082166 A354259 * A371007 A144003 A334775

Adjacent sequences: A370052 A370053 A370054 * A370056 A370057 A370058

Keyword

nonn

Author

Seiichi Manyama, Feb 08 2024

Status

approved