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A052793
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A simple grammar.
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0
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0, 0, 0, 0, 0, 0, 720, 5040, 23520, 90720, 312480, 997920, 3017520, 8751600, 24552528, 67026960, 178825920, 467812800, 1203094080, 3048024384, 7620293520
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,7
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 750
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FORMULA
| E.g.f.: x^4*exp(x)^2-2*x^4*exp(x)+x^4
Recurrence: {a(1)=0, a(2)=0, a(4)=0, a(3)=0, a(5)=0, a(6)=720, (2*n^2+6*n+4)*a(n)+(18-3*n^2+3*n)*a(n+1)+(n^2-5*n+6)*a(n+2)}
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MAPLE
| spec := [S, {B=Set(Z, 1 <= card), S=Prod(Z, Z, Z, Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A202095 A187290 A053625 * A179728 A052799 A153760
Adjacent sequences: A052790 A052791 A052792 * A052794 A052795 A052796
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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