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Search: id:A003085
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| A003085 |
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Number of connected digraphs with n nodes.
(Formerly M2067)
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+0
12
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| 1, 2, 13, 199, 9364, 1530843, 880471142, 1792473955306, 13026161682466252, 341247400399400765678, 32522568098548115377595264, 11366712907233351006127136886487, 14669074325902449468573755897547924182
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, pp. 124 and 241.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Keith Briggs, Table of n, a(n) for n = 1..64
P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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FORMULA
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a(n)=(1/n) *Sum_{d|n} mu(n/d)*A003084 (d), where mu is Moebius function.
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CROSSREFS
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Cf. A000273.
Sequence in context: A062156 A049512 A003507 this_sequence A053598 A102585 A078702
Adjacent sequences: A003082 A003083 A003084 this_sequence A003086 A003087 A003088
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 09 2000
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