OFFSET
0,4
FORMULA
a(n) = Sum_{k=1..n} (n-k)^(k-1) * Stirling2(n,k).
a(n) ~ n^(n-1) * (1 + exp(s)*s)^(n + 1/2) / (sqrt(exp(s)*(1 + s + s^2) - 1) * exp(n) * (1 + s)^(n - 1/2)), where s = 1.104072744884035178291292242554731... is the root of the equation 1 + s = (exp(-s) + s) * log(1 + exp(s)*s). - Vaclav Kotesovec, Nov 14 2022
E.g.f.: Series_Reversion( exp(-x) * log(1 + x * exp(x)) ). - Seiichi Manyama, Sep 09 2024
MATHEMATICA
Join[{0, 1}, Table[Sum[(n-k)^(k-1) * StirlingS2[n, k], {k, 1, n}], {n, 2, 20}]] (* Vaclav Kotesovec, Nov 14 2022 *)
PROG
(PARI) a(n) = sum(k=1, n, (n-k)^(k-1)*stirling(n, k, 2));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 27 2022
STATUS
approved