OFFSET
0,3
FORMULA
E.g.f.: 1 / (1 + exp(x) * x * (1 + 3*x + x^2)).
E.g.f.: 1 / (1 + Sum_{k>=1} k^3 * x^k / k!).
MATHEMATICA
a[0] = 1; a[n_] := a[n] = -Sum[Binomial[n, k] k^3 a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 20}]
nmax = 20; CoefficientList[Series[1/(1 + Exp[x] x (1 + 3 x + x^2)), {x, 0, nmax}], x] Range[0, nmax]!
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Jan 26 2021
STATUS
approved