OFFSET
0,3
FORMULA
E.g.f.: Series_Reversion( (1 - x)^2 * (exp(x) - 1) ).
a(n) = Sum_{k=1..n} (2*n+k-2)!/(2*n-1)! * Stirling1(n,k).
a(n) ~ LambertW(2*exp(1))^n * n^(n-1) / (sqrt(2*(1 + LambertW(2*exp(1)))) * exp(n) * (2 - LambertW(2*exp(1)))^(3*n - 1)). - Vaclav Kotesovec, Mar 29 2024
PROG
(PARI) my(N=20, x='x+O('x^N)); concat(0, Vec(serlaplace(serreverse((1-x)^2*(exp(x)-1)))))
(PARI) a(n) = sum(k=1, n, (2*n+k-2)!/(2*n-1)!*stirling(n, k, 1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 20 2024
STATUS
approved