OFFSET
0,3
FORMULA
a(n) = n! * [x^n] 1/(1 + n*x*exp(x)).
PROG
(PARI) a(n) = n!*sum(k=0, n, (-n)^(n-k)*(n-k)^k/k!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Feb 19 2022
STATUS
approved