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A054733
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Triangle of number of (weakly) connected unlabeled digraphs with n nodes and k arcs (n >=2, k >= 1).
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1
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1, 1, 0, 3, 4, 4, 1, 1, 0, 0, 8, 22, 37, 47, 38, 27, 13, 5, 1, 1, 0, 0, 0, 27, 108, 326, 667, 1127, 1477, 1665, 1489, 1154, 707, 379, 154, 61, 16, 5, 1, 1, 0, 0, 0, 0, 91, 582, 2432, 7694, 19646, 42148, 77305, 122953, 170315, 206982, 220768, 207301, 171008
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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REFERENCES
| F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973.
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EXAMPLE
| [ 1,1 ],[ 0,3,4,4,1,1 ],[ 0,0,8,22,37,47,38,27,13,5,1,1 ][ the last batch giving the numbers of connected digraphs with 4 nodes and from 1 to 12 arcs ].
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CROSSREFS
| Row sums give A003085.
Sequence in context: A021748 A132723 A057279 * A204255 A120649 A001009
Adjacent sequences: A054730 A054731 A054732 * A054734 A054735 A054736
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KEYWORD
| easy,nonn,tabf
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 21 2000
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