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Search: id:A052860
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| A052860 |
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A simple grammar: rooted sequences of cycles. |
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+0
2
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| 0, 1, 2, 9, 56, 440, 4164, 46046, 582336, 8288136, 131090880, 2280970032, 43298796672, 890441326320, 19720847692896, 467964024901200, 11844861486802944, 318549937907204352, 9070876711252816128
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 828
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FORMULA
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E.g.f.: -1/(-1+ln(-1/(-1+x)))*x
a(n) = n*A007840(n). a(n) = n!*Sum_{k=0..n-1} a(k)/k!/(n-k) for n>=1 with a(0)=0. - Paul D. Hanna (pauldhanna(AT)juno.com), Jul 19 2006
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MAPLE
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spec := [S, {C=Cycle(Z), B=Sequence(C), S=Prod(Z, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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PROGRAM
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(PARI) a(n)=n!*polcoeff(x/(1+log(1-x +x*O(x^n))), n) - Paul D. Hanna (pauldhanna(AT)juno.com), Jul 19 2006
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CROSSREFS
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Cf. A007840.
Sequence in context: A081004 A138740 A158883 this_sequence A052840 A036243 A033917
Adjacent sequences: A052857 A052858 A052859 this_sequence A052861 A052862 A052863
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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