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Search: id:A002031
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| A002031 |
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Number of labeled connected digraphs where every node has indegree 0 or outdegree 0 and no isolated nodes.
(Formerly M1707 N0676)
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+0
9
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| 2, 6, 38, 390, 6062, 134526, 4172198, 178449270, 10508108222, 853219059726, 95965963939958, 15015789392011590, 3282145108526132942, 1005193051984479922206, 432437051675617901246918
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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Also number of labeled connected graphs with 2-colored nodes with no isolated nodes where black nodes are only connected to white nodes and vice versa.
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REFERENCES
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Read, R. C.; Wright, E. M.; Colored graphs: A correction and extension. Canad. J. Math. 22 1970 594-596.
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LINKS
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N. J. A. Sloane, Transforms
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FORMULA
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Logarithmic transform of A052332.
E.g.f.: ln(Sum(exp((2^n-2)*x)*x^n/n!, n=0..infinity)). - Vladeta Jovovic (vladeta(AT)Eunet.yu), May 28 2004
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CROSSREFS
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Cf. A001831, A047863, A052332. Essentially the same as A002027.
Cf. A001832.
Sequence in context: A067106 A032111 A013703 this_sequence A005738 A055704 A005740
Adjacent sequences: A002028 A002029 A002030 this_sequence A002032 A002033 A002034
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KEYWORD
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nonn,nice
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AUTHOR
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njas
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EXTENSIONS
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More terms, formula and new title from Christian G. Bower (bowerc(AT)usa.net), Dec 15 1999.
Corrected by Vladeta Jovovic (vladeta(AT)Eunet.yu), Apr 12 2003
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