OFFSET
0,3
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 857
Maplesoft, Combstruct grammars.
FORMULA
G.f.: 1/(1 - x*g(x)) - 1 where g(x) is the g.f. of A052872. - Andrew Howroyd, Aug 09 2020
MAPLE
spec := [S, {B = Prod(Z, C), S=Sequence(B, 1 <= card), C=Set(S)}, unlabeled]:
seq(combstruct[count](spec, size=n), n=0..20);
PROG
(PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}
seq(n)={my(v=[]); for(n=1, n, v=Vec(1/(1-x-x^2*Ser(EulerT(v))) - 1)); concat([0], v)} \\ Andrew Howroyd, Aug 09 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
Terms a(21) and beyond from Andrew Howroyd, Aug 09 2020
STATUS
approved