OFFSET
0,3
FORMULA
a(n) = (1/(3*n+1)!) * Sum_{k=0..n} (3*n+k)! * |Stirling1(n,k)|.
a(n) ~ LambertW(3*exp(4))^n * n^(n-1) / (sqrt(3*(1 + LambertW(3*exp(4)))) * exp(n) * (-3 + LambertW(3*exp(4)))^(4*n + 1)). - Vaclav Kotesovec, Nov 07 2023
MATHEMATICA
Table[1/(3*n+1)! * Sum[(3*n+k)! * Abs[StirlingS1[n, k]], {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Nov 07 2023 *)
PROG
(PARI) a(n) = sum(k=0, n, (3*n+k)!*abs(stirling(n, k, 1)))/(3*n+1)!;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 06 2023
STATUS
approved