OFFSET
0,4
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..518
FORMULA
a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/(2^k * k! * (n - 2*k)!).
MATHEMATICA
With[{nn=30}, CoefficientList[Series[Exp[x Exp[x^2/2]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Mar 03 2024 *)
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x*(exp(x^2/2)))))
(PARI) a(n) = n!*sum(k=0, n\2, (n-2*k)^k/(2^k*k!*(n-2*k)!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 18 2022
STATUS
approved