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Search: id:A052677
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| A052677 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 3, 22, 246, 3672, 68520, 1534320, 40083120, 1196737920, 40196580480, 1500156806400, 61585275628800, 2758072531737600, 133812468652262400, 6991529043750451200, 391391124208051968000, 23371064978815217664000
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 625
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FORMULA
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E.g.f.: -(-1+x)/(1-4*x+x^2)
Recurrence: {a(0)=1, a(1)=3, (n^2+3*n+2)*a(n)+(-4*n-8)*a(n+1)+a(n+2)}
Sum(1/6*(1+_alpha)*_alpha^(-1-n), _alpha=RootOf(1-4*_Z+_Z^2))*n!
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MAPLE
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spec := [S, {S=Sequence(Union(Z, Prod(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: A141006 A042703 A141356 this_sequence A136741 A132693 A143634
Adjacent sequences: A052674 A052675 A052676 this_sequence A052678 A052679 A052680
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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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