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Search: id:A052581
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| A052581 |
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A simple regular expression in a labeled universe. |
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+0
2
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| 1, 0, 0, 0, 24, 120, 720, 5040, 80640, 1088640, 14515200, 199584000, 3353011200, 62270208000, 1220496076800, 24845812992000, 543992537088000, 12804747411456000, 320118685286400000, 8393511928209408000
(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 525
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FORMULA
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E.g.f.: (-1+x)/(-1+x^4+x)
Recurrence: {a(1)=0, a(0)=1, a(2)=0, a(3)=0, (-n^4-35*n^2-50*n-24-10*n^3)*a(n)+(-n-4)*a(n+3)+a(n+4)}
Sum(-1/283*(9+12*_alpha^3+16*_alpha^2-73*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z^4+_Z))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Z, Z, Z, Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Adjacent sequences: A052578 A052579 A052580 this_sequence A052582 A052583 A052584
Sequence in context: A052754 A050213 A124657 this_sequence A052605 A042120 A044356
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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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