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A126123
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Triangle read by rows: T(n,k) = number of edge-rooted unlabeled graphs having n nodes and k edges, n > 0, 0 < k <= n*(n-1)/2.
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0
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0, 1, 1, 1, 1, 1, 2, 4, 4, 2, 1, 1, 2, 6, 12, 16, 16, 12, 6, 2, 1, 1, 2, 7, 18, 40, 68, 96, 108, 96, 68, 40, 18, 7, 2, 1, 1, 2, 7, 20, 56, 135, 281, 500, 764, 982, 1068, 982, 764, 500, 281, 135, 56, 20, 7, 2, 1, 1, 2, 7, 21, 63, 181, 485, 1159, 2499, 4788, 8074, 11967, 15566
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,7
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REFERENCES
| F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973.
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EXAMPLE
| 0; 1; 1,1,1; 1,2,4,4,2,1; 1,2,6,12,16,16,12,6,2,1; ....
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CROSSREFS
| Sequence in context: A070512 A156283 A156346 * A096832 A016588 A160163
Adjacent sequences: A126120 A126121 A126122 * A126124 A126125 A126126
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KEYWORD
| nonn,tabf
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 07 2007
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