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Search: id:A052730
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| A052730 |
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A simple context-free grammar in a labeled universe. |
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1
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| 0, 0, 0, 6, 72, 1440, 35280, 1058400, 37376640, 1520830080, 70053984000, 3603888288000, 204806714112000, 12742502111539200, 861483843034214400, 62887137880799232000, 4929809613351727104000, 413044721987184967680000
(list; graph; listen)
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OFFSET
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0,4
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 686
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FORMULA
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E.g.f.: RootOf(-_Z+_Z^2+_Z^3+x)-RootOf(-_Z+_Z^2+_Z^3+x)^2-x
Recurrence: {a(1)=0, a(2)=0, a(3)=6, a(4)=72, (-105*n+135*n^3+30)*a(n)+(-130-107*n+29*n^2)*a(n+1)+(-99-91*n)*a(n+2)+15*a(n+3)}
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MAPLE
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spec := [S, {C=Prod(B, B), B=Union(S, Z, C), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A003235 A113133 A089252 this_sequence A010796 A038095 A012242
Adjacent sequences: A052727 A052728 A052729 this_sequence A052731 A052732 A052733
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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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