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Search: id:A052598
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| A052598 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 0, 4, 12, 144, 1200, 15840, 211680, 3467520, 61689600, 1241049600, 27223257600, 654316185600, 16999766784000, 476167826534400, 14282419447296000, 457079267893248000, 15539983733514240000
(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 543
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FORMULA
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E.g.f.: (-1+x)/(-1+x+2*x^2)
Recurrence: {a(1)=0, a(0)=1, (-2*n^2-6*n-4)*a(n)+(-2-n)*a(n+1)+a(n+2)}
Sum(1/9*(-1+5*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+2*_Z^2))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Sequence(Z), Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A002029 A152121 A077611 this_sequence A032071 A076030 A131491
Adjacent sequences: A052595 A052596 A052597 this_sequence A052599 A052600 A052601
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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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