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Search: id:A052718
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| A052718 |
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A simple context-free grammar in a labeled universe. |
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+0
1
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| 0, 1, 4, 24, 240, 3360, 60480, 1330560, 34594560, 1037836800, 35286451200, 1340885145600, 56317176115200, 2590590101299200, 129529505064960000, 6994593273507840000, 405686409863454720000, 25152557411534192640000
(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 674
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FORMULA
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E.g.f.: -x+1-(1-4*x)^(1/2)
Recurrence: {a(1)=1, a(2)=4, (2-4*n)*a(n)+a(n+1)}
4^(n+1)*GAMMA(n+3/2)/Pi^(1/2)
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MAPLE
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spec := [S, {B=Union(Z, C), C=Prod(B, B), S=Union(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A077555 A034256 A074598 this_sequence A061640 A126391 A006088
Adjacent sequences: A052715 A052716 A052717 this_sequence A052719 A052720 A052721
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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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