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A052884
Number of objects generated by the Combstruct grammar defined in the Maple program. See the link for the grammar specification.
1
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
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
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