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Search: id:A052585
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| A052585 |
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A simple regular expression in a labeled universe. |
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+0
2
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| 1, 1, 6, 30, 264, 2520, 30960, 428400, 6894720, 123742080, 2478470400, 54486432000, 1308153369600, 34005760588800, 952248474777600, 28566146568960000, 914137612996608000, 31080323154456576000
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Laguerre transform is A052563. [From Paul Barry (pbarry(AT)wit.ie), Aug 08 2008]
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 530
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FORMULA
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E.g.f.: -1/(-1+x+2*x^2)
Recurrence: {a(1)=1, a(0)=1, (-2*n^2-6*n-4)*a(n)+(-2-n)*a(n+1)+a(n+2)}
Sum(1/9*(1+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+2*_Z^2))*n!
a(n)=n!*A001045(n+1). [From Paul Barry (pbarry(AT)wit.ie), Aug 08 2008]
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MAPLE
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spec := [S, {S=Sequence(Union(Z, Prod(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: A009689 A133668 A121772 this_sequence A051821 A099031 A066108
Adjacent sequences: A052582 A052583 A052584 this_sequence A052586 A052587 A052588
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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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