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Search: id:A052697
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| A052697 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 0, 0, 6, 24, 0, 720, 10080, 40320, 362880, 10886400, 119750400, 958003200, 24908083200, 523069747200, 6538371840000, 125536739328000, 3556874280960000, 70426110763008000, 1338096104497152000
(list; graph; listen)
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OFFSET
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0,4
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 646
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FORMULA
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E.g.f.: -1/(-1+x^3+x^4)
Recurrence: {a(1)=0, a(0)=1, a(2)=0, a(3)=6, (-n^4-35*n^2-50*n-24-10*n^3)*a(n)+(-n^3-9*n^2-26*n-24)*a(n+1)+a(n+4)}
Sum(-1/283*(-16-73*_alpha+3*_alpha^2+12*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(-1+_Z^3+_Z^4))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Z, Union(Z, Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A013260 A013266 A154420 this_sequence A029592 A112034 A049319
Adjacent sequences: A052694 A052695 A052696 this_sequence A052698 A052699 A052700
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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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