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A054547 Triangular array giving number of labeled digraphs on n unisolated nodes and k=0...n*(n-1) arcs. 2
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; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..45.

FORMULA

a(n, k)=sum_{i=0..n} (-1)^(n-i)*C(n, i)*C(i*(i-1), k), k=0...n*(n-1).

EXAMPLE

[0],[0,2,1],[0,0,12,20,15,6,1],[0,0,12,140,435,768,920,792,495,220,66,12,1],...

CROSSREFS

Cf. A054548.

Sequence in context: A088632 A057272 A062735 * A202717 A291195 A025439

Adjacent sequences:  A054544 A054545 A054546 * A054548 A054549 A054550

KEYWORD

easy,nonn,tabf

AUTHOR

Vladeta Jovovic, Apr 09 2000

STATUS

approved

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Last modified October 23 17:32 EDT 2019. Contains 328373 sequences. (Running on oeis4.)