OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..420
FORMULA
a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/k!.
a(n) ~ n! * 2^(n/2) / ((1 + LambertW(2)) * LambertW(2)^(n/2)). - Vaclav Kotesovec, Nov 01 2022
MATHEMATICA
With[{nn=30}, CoefficientList[Series[1/(1-x Exp[x^2]), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Feb 14 2024 *)
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x*exp(x^2))))
(PARI) a(n) = n!*sum(k=0, n\2, (n-2*k)^k/k!);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Oct 29 2022
STATUS
approved