OFFSET
0,4
COMMENTS
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..250
FORMULA
E.g.f.: (exp(x^3/3)-1) * exp(x^2/2).
Recurrence: (n-3)*a(n) = (n-1)*(2*n-5)*a(n-2) + (n-3)*(n-2)*(n-1)*a(n-3) - (n-3)*(n-2)*(n-1)*a(n-4) - (n-4)*(n-3)*(n-2)*(n-1)*a(n-5). - Vaclav Kotesovec, Oct 09 2013
EXAMPLE
a(3) = 2: (2,3,1), (3,1,2).
MAPLE
egf:= (exp(x^3/3)-1)*exp(x^2/2):
a:= n-> n! *coeff(series(egf, x, n+1), x, n):
seq(a(n), n=0..30);
MATHEMATICA
A[n_, k_] := A[n, k] = If[n < 0, 0, If[n == 0, 1,
Sum[Product[n - i, {i, 1, j - 1}] A[n - j, k], {j, 2, k}]]];
T[n_, k_] := A[n, k] - If[k == 0, 0, A[n, k - 1]];
a[n_] := T[n, 3];
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 13 2013
STATUS
approved