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Search: id:A052505
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| A052505 |
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Number of labeled 3-constrained functional graphs. |
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+0
1
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| 1, 3, 300, 141120, 182952000, 505008504000, 2547446533632000
(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 38
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FORMULA
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E.g.f.: -2/(-2+x*RootOf(-6*_Z+6*x+x*_Z^3)^2)
Recurrence: {a(1)=0, (-9*n^4-54*n^3-117*n^2-108*n-36)*a(n)+(8*n+12)*a(n+3), a(2)=0, a(4)=0, a(3)=3, a(5)=0}
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MAPLE
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spec := [S, {g=Union(Z, Prod(Z, Set(g, card=3))), S=Set(Cycle(Prod(Z, Set(g, card=2))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A119059 A119049 A119067 this_sequence A071525 A157583 A085319
Adjacent sequences: A052502 A052503 A052504 this_sequence A052506 A052507 A052508
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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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