OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..100
MAPLE
A:= proc(n, k::nonnegint) option remember; if n<=0 or k=0 then 1 else A(n-1, k)(((x+1)^k-1)/k) fi; unapply(convert(series(exp (x*%), x, n+1), polynom), x) end: a:= n-> coeff(A(n, 2)(x), x, n)*n!: seq(a(n), n=0..21);
MATHEMATICA
A[n_, k_] := Module[{f}, f[x_] = If[n <= 0 || k == 0, 1, A[n-1, k][((x+1)^k-1)/k]]; Normal[Series[Exp[x*f[x]], { x, 0, n+1}]] /. x -> #]&; a[n_] := Coefficient[A[n, 2][x], x, n]*n!; Table[a[n], {n, 0, 21}] (* Jean-François Alcover, Feb 14 2014, after Maple *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 27 2008
STATUS
approved