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Search: id:A054547
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| A054547 |
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Triangular array giving number of labeled digraphs on n unisolated nodes and k=0...n*(n-1) arcs. |
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+0
3
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| 0, 0, 2, 1, 0, 0, 12, 20, 15, 6, 1, 0, 0, 12, 140, 435, 768, 920, 792, 495, 220, 66, 12, 1, 0, 0, 0, 240, 2520, 11604, 34150, 73560, 123495, 166860, 184426, 167900, 125965, 77520, 38760, 15504, 4845, 1140, 190, 20, 1
(list; graph; listen)
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OFFSET
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1,3
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FORMULA
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a(n, k)=sum_{i=0..n} (-1)^(n-i)*C(n, i)*C(i*(i-1), k), k=0...n*(n-1).
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EXAMPLE
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[0],[0,2,1],[0,0,12,20,15,6,1],[0,0,12,140,435,768,920,792,495,220,66,12,1],...
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CROSSREFS
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Cf. A054548.
Sequence in context: A088632 A057272 A062735 this_sequence A025439 A116852 A060154
Adjacent sequences: A054544 A054545 A054546 this_sequence A054548 A054549 A054550
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KEYWORD
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easy,nonn,tabf
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Apr 09 2000
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