A143567 E.g.f. satisfies A(x) = exp(x*A(x^3/3!)).
1, 1, 1, 1, 5, 21, 61, 211, 1401, 8065, 37241, 240021, 1997821, 14657501, 105629525, 958412911, 9201199281, 86311594881, 871038486001, 9432024424585, 106531641929781, 1271523772132741, 15583607760968941, 194983864950339851
Offset: 0
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 0..100
Programs
-
Maple
A:= proc(n) option remember; if n<=0 then 1 else unapply (convert (series (exp (x*A(n-3)(x^3/6)), x,n+1), polynom),x) fi end: a:= n-> coeff (A(n)(x), x,n)*n!: seq(a(n), n=0..29);
-
Mathematica
A[n_] := A[n] = If[n <= 0, 1&, Function[Normal[Series[Exp[y*A[n-2][y^3/3!]], {y, 0, n+1}] /. y -> #]]]; a[n_] := Coefficient [A[n][x], x, n]*n!; Table[a[n], {n, 0, 29}] (* Jean-François Alcover, Feb 13 2014, after Maple *)
Formula
a(0) = 1; a(n) = (n-1)! * Sum_{k=0..floor((n-1)/3)} (3*k+1) * a(k) * a(n-1-3*k) / (6^k * k! * (n-1-3*k)!). - Seiichi Manyama, Nov 28 2023
Comments