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A052825
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A simple grammar.
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0
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0, 0, 1, 3, 6, 11, 18, 31, 50, 85, 144, 251, 438, 789, 1420, 2601, 4792, 8907, 16618, 31219, 58814
(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 790
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FORMULA
| G.f.: -x/(-1+x)*Sum(numtheory[phi](j[1])/j[1]*ln((x^j[1]-1)/(2*x^j[1]-1)), j[1]=1 .. infinity)
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MAPLE
| spec := [S, {B=Cycle(C), C=Sequence(Z, 1 <= card), S=Prod(C, B)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A152074 A123629 A053992 * A003082 A058053 A091094
Adjacent sequences: A052822 A052823 A052824 * A052826 A052827 A052828
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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