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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). 10
 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, 136, 462, 972, 1412, 1639, 1485, 1152, 707, 379, 154, 61, 16, 5, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 REFERENCES F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973. LINKS R. W. Robinson, Counting strong digraphs (research announcement), J. Graph Theory 1, 1977, pp. 189-190. EXAMPLE [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. CROSSREFS Row sums give A003088. Cf. A057271-A057279. Sequence in context: A164612 A309748 A180401 * A057278 A010303 A046553 Adjacent sequences:  A057267 A057268 A057269 * A057271 A057272 A057273 KEYWORD more,nonn,tabf AUTHOR Vladeta Jovovic, Goran Kilibarda, Aug 23 2000 STATUS approved

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Last modified December 4 09:10 EST 2021. Contains 349484 sequences. (Running on oeis4.)