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Search: id:A052729
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| A052729 |
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A simple context-free grammar in a labeled universe. |
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+0
1
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| 0, 0, 2, 12, 168, 3120, 75600, 2237760, 78382080, 3169393920, 145297152000, 7446479040000, 421880659200000, 26181558769766400, 1766275594501017600, 128700516232544256000, 10073126652104355840000
(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 685
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FORMULA
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E.g.f.: RootOf(-_Z+_Z^2+_Z^3+x)^2
Recurrence: {a(1)=0, a(2)=2, a(3)=12, (21*n-27*n^3-6)*a(n)+(-49*n^2-6-65*n)*a(n+1)+(-33-17*n)*a(n+2)+5*a(n+3)}
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MAPLE
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spec := [S, {B=Prod(S, C), S=Prod(C, C), C=Union(B, S, Z)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A120958 A030163 A052728 this_sequence A098431 A059522 A113149
Adjacent sequences: A052726 A052727 A052728 this_sequence A052730 A052731 A052732
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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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