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A057278 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). 4

%I

%S 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,

%T 152,486,992,1419,1641,1485,1152,707,379,154,61,16,5,1,1

%N 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).

%D V. Jovovic, G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996), p. 246.

%e [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.

%Y Row sums give A049531. Cf. A057270-A057277, A057279.

%K more,nonn,tabf

%O 1,8

%A _Vladeta Jovovic_, Goran Kilibarda, Sep 14 2000

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Last modified January 22 05:19 EST 2022. Contains 350481 sequences. (Running on oeis4.)