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Search: id:A052688
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| A052688 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 0, 1, 2, 6, 48, 240, 1440, 15120, 120960, 1088640, 14515200, 159667200, 1916006400, 31135104000, 435891456000, 6538371840000, 125536739328000, 2134124568576000, 38414242234368000, 851515702861824000
(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 636
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FORMULA
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E.g.f.: x/(-1+x^3)/(-1+x)
Recurrence: {a(1)=1, a(0)=0, a(2)=2, (-39*n-29*n^2-9*n^3-n^4-18)*a(n)+(-n^2-5*n-6)*a(n+1)+(-n-3)*a(n+2)+(n+2)*a(n+3)}
(1/3*n+1/3+Sum(-1/9*(1+2*_alpha)*_alpha^(-1-n), _alpha=RootOf(_Z^2+_Z+1)))*n!
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(Z), Sequence(Prod(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: A052596 A098710 A052614 this_sequence A052657 A092143 A052593
Adjacent sequences: A052685 A052686 A052687 this_sequence A052689 A052690 A052691
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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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