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Search: id:A052754
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| 0, 0, 0, 0, 24, 120, 660, 4200, 30688, 254016, 2352240, 24108480, 271016064, 3316135680, 43877957760, 624306009600, 9505324339200, 154205312163840, 2655567756979200, 48382249157222400, 929788248840192000
(list; graph; listen)
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OFFSET
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0,5
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 710
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FORMULA
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E.g.f.: ln(-1/(-1+x))^2*x^2
Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, (n^4-6*n^2-n^3+4*n+8)*a(n)+(7*n-2*n^3+n^2-6)*a(n+1)+(n^2-n)*a(n+2)}
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MAPLE
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spec := [S, {B=Cycle(Z), S=Prod(B, B, Z, Z)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A052762 A099317 A052760 this_sequence A050213 A124657 A052581
Adjacent sequences: A052751 A052752 A052753 this_sequence A052755 A052756 A052757
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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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