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A052748
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A simple grammar.
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1
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0, 0, 0, 6, 36, 210, 1350, 9744, 78792, 708744, 7036200, 76521456, 905507856, 11589357312, 159580302336, 2352940786944, 36994905688320, 617953469022720, 10929614667747840, 204073497562936320
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 704
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FORMULA
| E.g.f.: ln(-1/(-1+x))^3
Recurrence: {a(1)=0, a(0)=0, a(2)=0, a(3)=6, (-1-3*n-3*n^2-n^3)*a(n+1)+(9*n+7+3*n^2)*a(n+2)+(-6-3*n)*a(n+3)+a(n+4)}
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MAPLE
| spec := [S, {B=Cycle(Z), S=Prod(B, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A096979 A123887 A105492 * A171280 A199525 A074436
Adjacent sequences: A052745 A052746 A052747 * A052749 A052750 A052751
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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