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Search: id:A003027
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| A003027 |
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Number of weakly connected digraphs with n nodes.
(Formerly M3161)
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+0
10
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| 1, 3, 54, 3834, 1027080, 1067308488, 4390480193904, 72022346388181584, 4721717643249254751360, 1237892809110149882059440768, 1298060596773261804821355107253504
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..30
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FORMULA
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a(n) = A062738(n)/2^n, since binary relations = digraphs with loops. - Ralf Stephan and Vladeta Jovovic, Mar 24 2004
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CROSSREFS
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Adjacent sequences: A003024 A003025 A003026 this_sequence A003028 A003029 A003030
Sequence in context: A091796 A006025 A049414 this_sequence A054545 A088278 A041155
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KEYWORD
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nonn,easy,nice
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AUTHOR
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njas
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EXTENSIONS
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Corrected and extended by Vladeta Jovovic, Goran Kilibarda (vladeta(AT)Eunet.yu).
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