OFFSET
0,3
LINKS
Eric Weisstein's World of Mathematics, Bell Polynomial.
Wikipedia, Touchard polynomials
FORMULA
E.g.f.: Sum_{k>=0} (k * x)^k / (k! * (1 + k * x)).
a(n) = n! * [x^n] B_n(x) * exp(x) / (1+x), where B_n(x) = Bell polynomials.
PROG
(PARI) a(n) = n!*sum(k=0, n, (-1)^(n-k)*k^n/k!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jan 04 2024
STATUS
approved