OFFSET
0,3
FORMULA
G.f.: Sum_{k>=0} (k^3 * x)^k/(1 + k^3 * x).
a(n) ~ 1/(1 + exp(-3)) * n^(3*n). - Vaclav Kotesovec, Dec 10 2021
MATHEMATICA
Join[{1}, Table[Sum[(-1)^(n-k) k^(3n), {k, 0, n}], {n, 20}]] (* Harvey P. Dale, Apr 12 2022 *)
PROG
(PARI) a(n) = sum(k=0, n, (-1)^(n-k)*k^(3*n));
(PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, (k^3*x)^k/(1+k^3*x)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Dec 05 2021
STATUS
approved