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Search: id:A121797
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| A121797 |
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Number of dissimilar forests on n nodes. |
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+0
1
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| 1, 1, 1, 3, 7, 21, 63, 203, 655, 2225, 7519, 26279, 91601, 326873, 1162873, 4215645, 15229413, 55842223, 204204265, 755626769, 2788876167, 10398436275, 38671589327, 145061791275, 542955212801, 2047149292105, 7702710310237
(list; graph; listen)
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OFFSET
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0,4
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REFERENCES
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Philippe Flajolet, Eric Fusy, Xavier Gourdon, Daniel Panario and Nicolas Pouyanne, A Hybrid of Darboux's Method and Singularity Analysis in Combinatorial Asymptotics, arXiv:math.CO/0606370
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..200
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FORMULA
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G.f.: Product_{n=1..infinity} (1+T_n x^n), where T_n (A000108) has g.f. (1-sqrt(1-4x))/2. - T. D. Noe (noe(AT)sspectra.com), Oct 08 2006
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MATHEMATICA
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nn=200; t=Rest[CoefficientList[Series[1-Sqrt[1-4x]/2, {x, 0, nn}], x]]; CoefficientList[Series[Product[(1+t[[k]]*x^k), {k, nn}], {x, 0, nn}], x] - T. D. Noe (noe(AT)sspectra.com), Oct 08 2006
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CROSSREFS
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Sequence in context: A148673 A141495 A151412 this_sequence A109361 A052805 A148674
Adjacent sequences: A121794 A121795 A121796 this_sequence A121798 A121799 A121800
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Oct 08 2006
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EXTENSIONS
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More terms from T. D. Noe (noe(AT)sspectra.com), Oct 08 2006
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