OFFSET
0,3
FORMULA
a(n) = (3*n)! * Sum_{k=0..n} (-1)^(n-k) * Stirling2(n,k)/(3*n-k+1)!.
PROG
(PARI) a(n) = (3*n)!*sum(k=0, n, (-1)^(n-k)*stirling(n, k, 2)/(3*n-k+1)!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Nov 07 2023
STATUS
approved