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