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A052861
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A simple grammar.
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1
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0, 0, 2, 15, 116, 1030, 10644, 127428, 1750944, 27325296, 479288160, 9355658400, 201405744000, 4743245520000, 121334466758400, 3350276227872000, 99309556729958400, 3145135939426252800
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 829
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FORMULA
| E.g.f.: -ln((-1+x)/(-1+2*x))*x/(-1+x)
Recurrence: {a(1)=0, a(0)=0, a(2)=2, (-2*n^4-12*n^3-22*n^2-12*n)*a(n)+(5*n^3+28*n^2+45*n+18)*a(n+1)+(-17*n-15-4*n^2)*a(n+2)+(n+2)*a(n+3)}
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MAPLE
| spec := [S, {B=Sequence(Z, 1 <= card), C=Cycle(B), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A052874 A074622 A031507 * A161937 A074621 A185758
Adjacent sequences: A052858 A052859 A052860 * A052862 A052863 A052864
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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