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Search: id:A052600
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| A052600 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 2, 10, 60, 504, 5040, 61200, 856800, 13749120, 247484160, 4953312000, 108972864000, 2615827737600, 68011521177600, 1904409771264000, 57132293137920000, 1828254303203328000, 62160646308913152000
(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 545
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FORMULA
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E.g.f.: 1/(-1+2*x)/(-1+x^2)
Recurrence: {a(0)=1, a(1)=2, a(2)=10, (12+2*n^3+12*n^2+22*n)*a(n)+(-n^2-5*n-6)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3)}
(4/3*2^n+Sum(-1/6*(2+_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z^2)))*n!
(4*2^n-1)/3*n! if n is even, (4*2^n-2)/3*n! otherwise.
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MAPLE
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spec := [S, {S=Prod(Sequence(Prod(Z, Z)), Sequence(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: A082042 A079856 A073329 this_sequence A092165 A107026 A107841
Adjacent sequences: A052597 A052598 A052599 this_sequence A052601 A052602 A052603
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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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