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Search: id:A052589
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| A052589 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 0, 1, 6, 42, 360, 3720, 45360, 640080, 10281600, 185431680, 3712262400, 81709689600, 1961511552000, 51005527372800, 1428241944729600, 42848566016256000, 1371175035310080000, 46620306887970816000
(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 534
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FORMULA
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E.g.f.: x/(-1+2*x)/(-1+x)
Recurrence: {a(1)=1, a(0)=0, (2*n^2+6*n+4)*a(n)+(-6-3*n)*a(n+1)+a(n+2)}
(2^n-1)*n!
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(Z), Sequence(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: A132804 A074017 A135887 this_sequence A074107 A052608 A098461
Adjacent sequences: A052586 A052587 A052588 this_sequence A052590 A052591 A052592
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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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