A327411 a(n) = multinomial(2*n+3; 3, 2, 2, ..., 2) (n times '2').

1, 10, 210, 7560, 415800, 32432400, 3405402000, 463134672000, 79196028912000, 16631166071520000, 4207685016094560000, 1262305504828368000000, 443069232194757168000000, 179886108271071410208000000, 83647040346048205746720000000, 44165637302713452634268160000000

Offset

0,2

Links

Table of n, a(n) for n=0..15.

Formula

a(n) = 2^(-n-1)*Gamma(2*n + 4)/3.

a(n) = (2*(n-1)^2 + 9*n + 1)*a(n-1) for n > 0.

a(n) / n! = A000457(n).

Maple

a:= n-> combinat[multinomial](2*n+3, 3, 2$n):
seq(a(n), n=0..17);  # Alois P. Heinz, Sep 07 2019

Prog

(SageMath)
def a(n):
    return multinomial([3] + [2] * n)
[a(n) for n in range(20)]

Crossrefs

Cf. A000457, A327412.

Sequence in context: A238467 A254322 A365341 * A112364 A201621 A057408

Adjacent sequences: A327408 A327409 A327410 * A327412 A327413 A327414

Keyword

nonn

Author

Peter Luschny, Sep 07 2019

Status

approved