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Search: id:A052575
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| A052575 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 1, 8, 48, 528, 6240, 95040, 1632960, 32578560, 725760000, 18027878400, 491774976000, 14645952921600, 472356889804800, 16409046682828800, 610694391250944000, 24244324628299776000, 1022626965270822912000
(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 518
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FORMULA
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E.g.f.: -(-1+x)/(1-2*x-2*x^2+2*x^3)
Recurrence: {a(1)=1, a(0)=1, a(2)=8, (12+2*n^3+12*n^2+22*n)*a(n)+(-2*n^2-10*n-12)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3)}
Sum(-1/37*(-5+9*_alpha^2-12*_alpha)*_alpha^(-1-n), _alpha=RootOf(2*_Z^3-2*_Z^2-2*_Z+1))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A165506 A165748 A072169 this_sequence A108214 A010568 A080493
Adjacent sequences: A052572 A052573 A052574 this_sequence A052576 A052577 A052578
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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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