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A052851
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A simple grammar.
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2
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0, 1, 3, 20, 220, 3424, 69008, 1706256, 49956240, 1689497376, 64799254752, 2778906776832, 131756614920192, 6843405231815424, 386414606189283072, 23567401521343170048, 1543994621969805135360, 108137637714495023354880
(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 819
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FORMULA
| E.g.f.: 1/2-1/2*(1-4*ln(-1/(-1+x)))^(1/2)
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MAPLE
| spec := [S, {B=Cycle(Z), S=Prod(B, C), C=Sequence(S)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A006963 A113333 A206405 * A058477 A119758 A108527
Adjacent sequences: A052848 A052849 A052850 * A052852 A052853 A052854
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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