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Search: id:A052682
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| A052682 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 0, 6, 18, 288, 2520, 41040, 604800, 11733120, 236234880, 5530291200, 138790713600, 3855483878400, 115075344384000, 3716149018982400, 128239702246656000, 4727462529613824000, 185010460036706304000
(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 630
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FORMULA
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E.g.f.: (-1+x)/(-1+x+3*x^2)
Recurrence: {a(1)=0, a(0)=1, (-3*n^2-9*n-6)*a(n)+(-2-n)*a(n+1)+a(n+2)}
Sum(1/13*(-1+7*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+3*_Z^2))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Sequence(Z), Union(Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A052634 A059944 A052139 this_sequence A130437 A119813 A119986
Adjacent sequences: A052679 A052680 A052681 this_sequence A052683 A052684 A052685
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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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