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Search: id:A052738
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| A052738 |
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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, 120, 1920, 40320, 1028160, 30965760, 1077753600, 42551308800, 1878484608000, 91686654259200, 4902558383923200, 284994551761920000, 17895345882365952000, 1207064057173438464000, 87041570211234422784000
(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 694
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FORMULA
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E.g.f.: RootOf(-_Z+_Z^4+_Z^2+x)^2
Recurrence: {a(1)=0, a(2)=2, a(3)=12, (9216*n^3-2496*n-576+1152*n^2+6144*n^4)*a(n)+(-9096-30320*n-28032*n^2-7936*n^3)*a(n+1)+(15488*n+6272*n^2+10404)*a(n+2)+(-3784*n-7600)*a(n+3)+589*a(n+4), a(4)=120}
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MAPLE
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spec := [S, {B=Union(S, Z, C), S=Prod(B, B), C=Prod(S, S)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A131815 A047793 A048800 this_sequence A007132 A138534 A062080
Adjacent sequences: A052735 A052736 A052737 this_sequence A052739 A052740 A052741
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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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