OFFSET
0,3
FORMULA
a(n) = (1/(2*n+1)!) * Sum_{k=0..n} (2*n+k)! * Stirling2(n,k).
a(n) ~ 2^(n-1) * LambertW(exp(1/2))^(2*n + 1) * n^(n-1) / (sqrt(1 + LambertW(exp(1/2))) * exp(n) * (2*LambertW(exp(1/2)) - 1)^(3*n + 1)). - Vaclav Kotesovec, Nov 07 2023
MATHEMATICA
Table[1/(2*n+1)! * Sum[(2*n+k)! * StirlingS2[n, k], {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Nov 07 2023 *)
PROG
(PARI) a(n) = sum(k=0, n, (2*n+k)!*stirling(n, k, 2))/(2*n+1)!;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 06 2023
STATUS
approved