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A057270
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Triangle T(n,k) of number of unilaterally connected digraphs on n unlabeled nodes with k arcs, k=0..n*(n-1).
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10
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1, 0, 1, 1, 0, 0, 1, 4, 4, 1, 1, 0, 0, 0, 1, 10, 30, 45, 38, 27, 13, 5, 1, 1, 0, 0, 0, 0, 1, 20, 136, 462, 972, 1412, 1639, 1485, 1152, 707, 379, 154, 61, 16, 5, 1, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,8
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REFERENCES
| F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973.
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LINKS
| R. W. Robinson, Counting strong digraphs (research announcement), J. Graph Theory 1, 1977, pp. 189-190.
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EXAMPLE
| [1],[0,1,1],[0,0,1,4,4,1,1],[0,0,0,1,10,30,45,38,27,13,5,1,1],...; Number of unilaterally connected digraphs on 4 unlabeled nodes is 171=1+10+30+45+38+27+13+5+1+1.
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CROSSREFS
| Row sums give A003088. Cf. A057271-A057279.
Sequence in context: A163353 A164612 A180401 * A057278 A010303 A046553
Adjacent sequences: A057267 A057268 A057269 * A057271 A057272 A057273
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KEYWORD
| more,nonn
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AUTHOR
| Vladeta Jovovic, Goran Kilibarda (vladeta(AT)eunet.rs), Aug 23 2000
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