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Search: id:A052700
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| A052700 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 0, 1, 4, 36, 432, 6480, 116640, 2449440, 58786560, 1587237120, 47617113600, 1571364748800, 56569130956800, 2206196107315200, 92660236507238400, 4169710642825728000, 200146110855634944000, 10207451653637382144000
(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 650
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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, a(2)=4, (-3*n-3)*a(n)+a(n+1)}
2/9*3^n*n!
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(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: A002894 A131765 A132864 this_sequence A167540 A136224 A009533
Adjacent sequences: A052697 A052698 A052699 this_sequence A052701 A052702 A052703
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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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