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A052804
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A simple grammar: cycles of rooted cycles.
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0
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0, 0, 2, 3, 20, 90, 714, 5460, 54704, 580608, 7214040, 96932880, 1452396912, 23507621280, 414102201408, 7827185489760, 158757800613120, 3429996441661440, 78775916315263488, 1914627403408320000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 765
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FORMULA
| G.f.: ln(-1/(-1+ln(-1/(-1+x))*x))
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MAPLE
| spec := [S, {B=Prod(C, Z), C=Cycle(Z), S=Cycle(B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A087301 A007113 A066166 * A125763 A042441 A128977
Adjacent sequences: A052801 A052802 A052803 * A052805 A052806 A052807
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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