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Search: id:A052665
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| A052665 |
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a(0)=0, for n >= 1, a(n) = ((2^(n-1)-1)*n!. |
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+0
1
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| 0, 0, 2, 18, 168, 1800, 22320, 317520, 5120640, 92534400, 1854316800, 40834886400, 980516275200, 25499650176000, 714077383219200, 21423629170944000, 685577056260096000, 23309975600271360000
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 612
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FORMULA
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E.g.f.: x^2/((1-x)*(1-2*x)).
Recurrence: {a(1)=0, a(0)=0, a(2)=2, (2*n^2+6*n+4)*a(n)+(-6-3*n)*a(n+1)+a(n+2)}
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MAPLE
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spec := [S, {S=Prod(Z, Z, Sequence(Z), Sequence(Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A037623 A052865 A052883 this_sequence A092473 A073558 A132306
Adjacent sequences: A052662 A052663 A052664 this_sequence A052666 A052667 A052668
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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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