OFFSET
0,3
MAPLE
p := n -> local k; add(k!*abs(Stirling1(n, k))*x^k, k = 0..n):
a := n -> local j; add(subs(x=j, p(n - j)), j = 0..n):
seq(a(n), n = 0..20);
MATHEMATICA
p[n_][x_] := Sum[k!*Abs[StirlingS1[n, k]]*If[k == 0, 1, x^k], {k, 0, n}];
a[n_] := Sum[p[n - j][j], {j, 0, n}];
Table[a[n], {n, 0, 20}] (* Jean-François Alcover, May 12 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Apr 29 2024
STATUS
approved