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Search: id:A052624
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| A052624 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 2, 8, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000, 20922789888000, 355687428096000, 6402373705728000, 121645100408832000, 2432902008176640000
(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 570
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FORMULA
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E.g.f.: (1+x^2-2*x^3+x^4)/(-1+x)^2
Recurrence: {a(0)=1, a(1)=2, a(2)=8, a(3)=24, (-2-n)*a(n)+a(n+1), a(4)=120}
(n+1)*n!
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MAPLE
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spec := [S, {S=Union(Prod(Sequence(Z), Sequence(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: A150668 A150669 A123775 this_sequence A087982 A145238 A093458
Adjacent sequences: A052621 A052622 A052623 this_sequence A052625 A052626 A052627
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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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