OFFSET
0,2
FORMULA
E.g.f.: 1 / (2 * (1 - 2*x) - exp(x)).
a(n) ~ n! * 2^(n-1) / ((1 + LambertW(exp(1/2)/4)) * (1 - 2*LambertW(exp(1/2)/4))^(n+1)). - Vaclav Kotesovec, Jun 20 2022
MATHEMATICA
a[0] = 1; a[n_] := a[n] = 4 n a[n - 1] + Sum[Binomial[n, k] a[k], {k, 0, n - 1}]; Table[a[n], {n, 0, 18}]
nmax = 18; CoefficientList[Series[1/(2 (1 - 2 x) - Exp[x]), {x, 0, nmax}], x] Range[0, nmax]!
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 25 2021
STATUS
approved