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A052758
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A simple grammar.
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0
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0, 0, 0, 0, 24, 180, 1260, 9450, 77952, 709128, 7087440, 77398200, 918257472, 11771602128, 162251002368, 2393704535040, 37647052591104, 628913396701440, 11123162442408960, 207662678687208960
(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 714
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FORMULA
| E.g.f.: ln(-1/(-1+x))^3*x
Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, (4*n^4-n^6-7*n-9*n^2-3*n^5+6+10*n^3)*a(n)+(3*n^5+12*n^4+4*n^3-13*n^2+6*n)*a(n+1)+(-12*n^3-3*n^4-9*n^2)*a(n+2)+(n^3+3*n^2+2*n)*a(n+3)}
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MAPLE
| spec := [S, {B=Cycle(Z), S=Prod(B, B, B, Z)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A165187 A052761 A073993 * A143040 A128960 A047057
Adjacent sequences: A052755 A052756 A052757 * A052759 A052760 A052761
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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