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A057270 Triangle T(n,k) of number of unilaterally connected digraphs on n unlabeled nodes with k arcs, k=0..n*(n-1). 8

%I

%S 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,

%T 136,462,972,1412,1639,1485,1152,707,379,154,61,16,5,1,1

%N Triangle T(n,k) of number of unilaterally connected digraphs on n unlabeled nodes with k arcs, k=0..n*(n-1).

%D F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973.

%H R. W. Robinson, <a href="http://dx.doi.org/10.1002/jgt.3190010215">Counting strong digraphs (research announcement)</a>, J. Graph Theory 1, 1977, pp. 189-190.

%e [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.

%Y Row sums give A003088. Cf. A057271-A057279.

%K more,nonn,tabf

%O 1,8

%A _Vladeta Jovovic_, Goran Kilibarda, Aug 23 2000

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Last modified January 23 03:15 EST 2022. Contains 350504 sequences. (Running on oeis4.)