OFFSET
0,4
FORMULA
a(n) = n! * Sum_{j=0..n} Sum_{k=0..floor(j/2)} binomial(j-k,n-j-k) * Stirling1(j-k,k)/(j-k)!.
PROG
(PARI) a(n) = n!*sum(j=0, n, sum(k=0, j\2, binomial(j-k, n-j-k)*stirling(j-k, k, 1)/(j-k)!));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Mar 14 2024
STATUS
approved