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A057278
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Triangle T(n,k) of number of digraphs with a source and a sink on n unlabeled nodes and k arcs, k=0,1,..,n*(n-1).
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2
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1, 0, 1, 1, 0, 0, 1, 4, 4, 1, 1, 0, 0, 0, 1, 11, 31, 45, 38, 27, 13, 5, 1, 1, 0, 0, 0, 0, 1, 23, 152, 486, 992, 1419, 1641, 1485, 1152, 707, 379, 154, 61, 16, 5, 1, 1
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listen;
history;
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internal format)
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OFFSET
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1,8
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REFERENCES
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V. Jovovic, G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996), p. 246.
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LINKS
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Table of n, a(n) for n=1..45.
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EXAMPLE
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[1],[0,1,1],[0,0,1,4,4,1,1],[0,0,0,1,11,31,45,38,27,13,5,1,1],...; Number of digraphs with a source and a sink on 3 unlabeled nodes is 11=1+4+4+1+1.
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CROSSREFS
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Row sums give A049531. Cf. A057270-A057277, A057279.
Sequence in context: A164612 A180401 A057270 * A010303 A046553 A046552
Adjacent sequences: A057275 A057276 A057277 * A057279 A057280 A057281
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KEYWORD
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more,nonn,tabf
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AUTHOR
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Vladeta Jovovic, Goran Kilibarda (vladeta(AT)eunet.rs), Sep 14 2000
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STATUS
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approved
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