A052891 Number of objects generated by the Combstruct grammar defined in the Maple program. See the link for the grammar specification.

0, 1, 2, 5, 16, 56, 217, 876, 3686, 15903, 70103, 314042, 1426076, 6548060, 30352695, 141837086, 667469159, 3160370217, 15045244375, 71970393570, 345766441537, 1667629158127, 8071308125136, 39190243658297, 190845259909328, 931856232714004, 4561292365652751

Offset: 0

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

• easy
• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..200
• INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 867
• Maplesoft, Combstruct grammars.

Crossrefs

Cf. A052893.

Programs

Maple

spec := [S, {C=Prod(Z,B), S=Set(C,1 <= card), B=Sequence(S)}, unlabeled]:
seq(combstruct[count](spec,size=n), n=0..20);

PARI

EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
seq(n)={my(v=[0]); for(n=1, n, v=concat([0],EulerT(Vec(1/(1-Ser(v)))))); v} \\ Andrew Howroyd, Aug 09 2020

Formula

G.f.: 1 - 1/g(x) where g(x) is the g.f. of A052893. - Andrew Howroyd, Aug 09 2020

Extensions

Terms a(21) and beyond from Andrew Howroyd, Aug 09 2020