OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} (n+3*k)!/(n+2*k+1)! * Stirling1(n,k).
MATHEMATICA
Table[Sum[(n+3*k)!/(n+2*k+1)! * StirlingS1[n, k], {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Nov 10 2023 *)
PROG
(PARI) a(n) = sum(k=0, n, (n+3*k)!/(n+2*k+1)!*stirling(n, k, 1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 07 2023
STATUS
approved