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A052732
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A simple context-free grammar in a labeled universe.
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0
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0, 0, 0, 0, 24, 240, 3600, 70560, 1693440, 47900160, 1556755200, 57081024000, 2328905779200, 104589041356800, 5124863026483200, 272011960636416000, 15543540607795200000, 951264685197066240000, 62070020709108572160000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 688
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FORMULA
| E.g.f.: (1/2-x-1/2*(1-4*x)^(1/2))*x^2
Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, (-4*n^2+6*n+10)*a(n)+(n-1)*a(n+1), a(5)=240}
{a(1)=0, a(n+5)=0}
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MAPLE
| spec := [S, {B=Union(Z, C), C=Prod(B, B), S=Prod(Z, Z, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A000536 A151720 A052652 * A086603 A000594 A022716
Adjacent sequences: A052729 A052730 A052731 * A052733 A052734 A052735
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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