OFFSET
0,3
FORMULA
log(a(n)) ~ n *(2*log(n) - log(log(n)) - 2 + (log(log(n)) + log(log(n)-1) + 1)/log(n)). - Vaclav Kotesovec, Feb 19 2022
MATHEMATICA
Join[{1}, Table[n!*Sum[k^(n-k) * (n-k)^k/k!, {k, 0, n}], {n, 1, 20}]] (* Vaclav Kotesovec, Feb 19 2022 *)
PROG
(PARI) a(n) = n!*sum(k=0, n, k^(n-k)*(n-k)^k/k!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 18 2022
STATUS
approved