OFFSET
0,3
FORMULA
a(n) = n! * Sum_{k=0..floor(n/2)} (n-3*k+1)^(k-1) * Stirling2(n-k,k)/(n-k)!.
PROG
(PARI) a(n) = n!*sum(k=0, n\2, (n-3*k+1)^(k-1)*stirling(n-k, k, 2)/(n-k)!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Sep 02 2022
STATUS
approved