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Search: id:A052801
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| A052801 |
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A simple grammar: labeled pairs of sequences of cycles. |
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+0
1
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| 1, 2, 8, 46, 342, 3108, 33324, 411360, 5741856, 89379120, 1534623936, 28804923024, 586686138384, 12885385945248, 303537419684064, 7633673997722496, 204125888803996800, 5782960189212871680
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 759
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FORMULA
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E.g.f.: 1/(-1+ln(-1/(-1+x)))^2
a(n) = Sum_{k=0..n} (-1)^(n-k)*Stirling1(n, k)*(k+1)!. - Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 21 2003
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MAPLE
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spec := [S, {C=Cycle(Z), B=Sequence(C), S=Prod(B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Adjacent sequences: A052798 A052799 A052800 this_sequence A052802 A052803 A052804
Sequence in context: A088791 A111552 A128085 this_sequence A074599 A007289 A099765
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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