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Search: id:A052711
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| A052711 |
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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, 0, 6, 48, 600, 10080, 211680, 5322240, 155675520, 5189184000, 194075481600, 8045310873600, 366061644748800, 18134130709094400, 971471287987200000, 55956746188062720000, 3448334483839365120000
(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 667
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FORMULA
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E.g.f.: -(-1/2+1/2*(1-4*x)^(1/2)+x)*x
Recurrence: {a(1)=0, a(2)=0, a(3)=6, a(4)=48, (2*n+6-4*n^2)*a(n)+a(n+1)*n}
0
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MAPLE
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spec := [S, {C=Union(B, Z), B=Prod(C, C), S=Prod(B, Z)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Adjacent sequences: A052708 A052709 A052710 this_sequence A052712 A052713 A052714
Sequence in context: A052567 A002170 A052731 this_sequence A113388 A113393 A138426
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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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