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Search: id:A052698
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| A052698 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 0, 1, 8, 78, 960, 14520, 262080, 5508720, 132249600, 3571102080, 107136691200, 3535550726400, 127280305152000, 4963938127948800, 208485488552140800, 9381848292520704000, 450328738963783680000, 22966766042840395776000
(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 648
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FORMULA
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E.g.f.: x/(-1+x)/(-1+3*x)
Recurrence: {a(1)=1, a(0)=0, (3*n^2+9*n+6)*a(n)+(-4*n-8)*a(n+1)+a(n+2)}
(-1/2+1/2*3^n)*n!
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(Z), Sequence(Union(Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A132164 A058480 A000435 this_sequence A052603 A071556 A145508
Adjacent sequences: A052695 A052696 A052697 this_sequence A052699 A052700 A052701
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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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