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Search: id:A052658
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| A052658 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 1, 4, 30, 264, 3000, 40320, 635040, 11410560, 230791680, 5185555200, 128172844800, 3455996544000, 100952461209600, 3175730791833600, 107037070043904000, 3848161361780736000, 146994587721805824000
(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 605
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FORMULA
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E.g.f.: (-1+x^2)*(-1+x)/(x^3-x^2-2*x+1)
Recurrence: {a(1)=1, a(0)=1, a(2)=4, (n^3+6*n^2+11*n+6)*a(n)+(-n^2-5*n-6)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3), a(3)=30}
Sum(-1/7*(_alpha+_alpha^2-2)*_alpha^(-1-n), _alpha=RootOf(_Z^3-_Z^2-2*_Z+1))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Sequence(Z), Sequence(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: A086452 A091527 A102307 this_sequence A127130 A052631 A167139
Adjacent sequences: A052655 A052656 A052657 this_sequence A052659 A052660 A052661
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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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