OFFSET
0,3
COMMENTS
Euler transform of A036249 (as well as first differences thereof). - Franklin T. Adams-Watters, Feb 08 2006
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1717
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 823
FORMULA
G.f. satisfies A(x) = exp( Sum_{n>=1} A(x^n)/(1-x^n) * x^n/n ). - Paul D. Hanna, Oct 26 2011
G.f.: A(x) = Sum_{k>=0} a(k) * x^k = 1/Product_{j>=1} Product_{k>=0} (1-x^(j+k))^a(k). - Seiichi Manyama, Jun 07 2023
MAPLE
spec := [S, {B=Sequence(Z, 1 <= card), S=Set(C), C=Prod(B, S)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
max = 26; A[_] = 1; Do[A[x_] = Exp[Sum[A[x^k]/(1 - x^k)*x^k/k + O[x]^n, {k, 1, n}]] // Normal, {n, 1, max}]; CoefficientList[A[x] + O[x]^max, x] (* Jean-François Alcover, May 25 2018 *)
PROG
(PARI) {a(n)=my(A=1+x); for(i=1, n, A=exp(sum(m=1, n, subst(A/(1-x), x, x^m+x*O(x^n))*x^m/m))); polcoeff(A, n)} /* Paul D. Hanna, Oct 26 2011 */
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
More terms from Franklin T. Adams-Watters, Feb 08 2006
STATUS
approved