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Search: id:A052630
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| A052630 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 4, 34, 432, 7320, 155040, 3940560, 116847360, 3959786880, 150965337600, 6394994323200, 297985937356800, 15147464243788800, 834153946904678400, 49469459519031552000, 3143339899991875584000, 213046423884047609856000
(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 576
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FORMULA
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E.g.f.: -1/(-1+4*x+x^2)
Recurrence: {a(0)=1, a(1)=4, (-2-n^2-3*n)*a(n)+(-4*n-8)*a(n+1)+a(n+2)}
Sum(1/10*(2+_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, Z, Z, Z, 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: A141007 A158839 A145349 this_sequence A071213 A052629 A151919
Adjacent sequences: A052627 A052628 A052629 this_sequence A052631 A052632 A052633
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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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