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A052864
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A simple grammar.
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1
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0, 0, 2, 12, 82, 670, 6458, 72072, 915864, 13068768, 206998032, 3604604256, 68455569840, 1408152976464, 31191374639280, 740216664633984, 18736923967232256, 503916672279712896, 14349543617967990912
(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 832
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FORMULA
| E.g.f.: -ln(-1/(-1+x))^2/(-1+ln(-1/(-1+x)))
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MAPLE
| spec := [S, {C=Cycle(Z), B=Sequence(C, 1 <= card), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Cf. A009122.
Sequence in context: A055548 A092850 A199420 * A136278 A130464 A006657
Adjacent sequences: A052861 A052862 A052863 * A052865 A052866 A052867
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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