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Search: id:A052587
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| A052587 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 0, 0, 2, 6, 48, 480, 5760, 80640, 1290240, 23224320, 464486400, 10218700800, 245248819200, 6376469299200, 178541140377600, 5356234211328000, 171399494762496000, 5827582821924864000, 209792981589295104000
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Essentially the same as A051578. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 22 2008
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 532
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FORMULA
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E.g.f.: x^2*(-1+x)/(-1+2*x)
Recurrence: {a(1)=0, a(0)=0, a(3)=6, a(2)=2, (-2*n-2)*a(n)+a(n+1)}
1/8*2^n*n!
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MAPLE
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spec := [S, {S=Prod(Z, Z, Sequence(Prod(Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A052586 A052554 A052743 this_sequence A052735 A052717 A129464
Adjacent sequences: A052584 A052585 A052586 this_sequence A052588 A052589 A052590
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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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