OFFSET
0,4
FORMULA
a(0) = 1; a(n) = Sum_{k=1..n} (k! - 1) * binomial(n,k) * a(n-k).
a(n) ~ n! * (1-r)^2 / ((1 - (1-r)*r) * r^(n+1)), where r = 0.65904606840740666... is the root of the equation exp(r)*(1-r) = r. - Vaclav Kotesovec, Jul 21 2022
MATHEMATICA
m = 20; Range[0, m]! * CoefficientList[Series[1/(Exp[x] - x/(1 - x)), {x, 0, m}], x] (* Amiram Eldar, Mar 11 2022 *)
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(1/(exp(x)-x/(1-x))))
(PARI) a(n) = if(n==0, 1, sum(k=1, n, (k!-1)*binomial(n, k)*a(n-k)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 11 2022
STATUS
approved