A052884 Number of objects generated by the Combstruct grammar defined in the Maple program. See the link for the grammar specification.

0, 1, 2, 6, 20, 73, 278, 1106, 4519, 18908, 80530, 348144, 1523492, 6736163, 30046395, 135041458, 610954709, 2780185203, 12716659506, 58434130086, 269618874220, 1248677115180, 5802514845319, 27046974876433, 126428233339972, 592506121687352, 2783409839422829

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

Cf. A052872.

Sequence in context: A150138 A148481 A150139 * A150140 A061396 A230823

Adjacent sequences: A052881 A052882 A052883 * A052885 A052886 A052887

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