OFFSET
0,2
FORMULA
E.g.f.: B(x)^3, where B(x) is the e.g.f. of A377892.
a(n) = 3 * n! * Sum_{k=0..n} (2*n+3)^(k-1) * binomial(2*n+3,n-k)/k!.
a(n) == 0 (mod 3) for n>0.
PROG
(PARI) a(n) = 3*n!*sum(k=0, n, (2*n+3)^(k-1)*binomial(2*n+3, n-k)/k!);
CROSSREFS
KEYWORD
nonn,new
AUTHOR
Seiichi Manyama, Jan 07 2025
STATUS
approved