OFFSET
0,3
FORMULA
a(n) = n! * Sum_{k=0..floor(n/2)} k! * binomial(4,k) * |Stirling1(n-k,k)|/(n-k)!.
PROG
(PARI) a(n) = n!*sum(k=0, n\2, k!*binomial(4, k)*abs(stirling(n-k, k, 1))/(n-k)!);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Nov 04 2024
STATUS
approved