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Search: id:A123554
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| A123554 |
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Triangle read by rows: T(n,k) = number of labeled loopless digraphs with n nodes and k arcs (n >= 1, 0 <= k <= n*(n-1)). |
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+0
1
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| 1, 1, 2, 1, 1, 6, 15, 20, 15, 6, 1, 1, 12, 66, 220, 495, 792, 924, 792, 495, 220, 66, 12, 1, 1, 20, 190, 1140, 4845, 15504, 38760, 77520, 125970, 167960, 184756, 167960, 125970, 77520, 38760, 15504, 4845, 1140, 190, 20, 1, 1, 30, 435, 4060, 27405, 142506, 593775
(list; graph; listen)
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OFFSET
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1,3
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REFERENCES
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J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 521.
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EXAMPLE
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Triangle begins:
1
1 2 1
1 6 15 20 15 6 1
1 12 66 220 495 792 924 792 495 220 66 12 1
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CROSSREFS
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Cf. A052283 (unlabeled analogue).
Sequence in context: A165891 A039763 A094262 this_sequence A025270 A144510 A143670
Adjacent sequences: A123551 A123552 A123553 this_sequence A123555 A123556 A123557
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KEYWORD
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nonn,tabf
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Nov 15 2006
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EXTENSIONS
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More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 15 2006
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