OFFSET
0,5
FORMULA
a(n) = n! * Sum_{j=0..n} Sum_{k=0..floor(j/3)} binomial(j-2*k,n-j-k) * Stirling1(j-2*k,k)/(j-2*k)!.
PROG
(PARI) a(n) = n!*sum(j=0, n, sum(k=0, j\3, binomial(j-2*k, n-j-k)*stirling(j-2*k, k, 1)/(j-2*k)!));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Mar 14 2024
STATUS
approved