This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A057272 #10 Feb 05 2015 07:12:03 %S A057272 1,0,2,1,0,0,12,20,15,6,1,0,0,0,104,426,768,920,792,495,220,66,12,1,0, %T A057272 0,0,0,1160,9184,32420,73000,123425,166860,184426,167900,125965,77520, %U A057272 38760,15504,4845,1140,190,20,1 %N A057272 Triangle T(n,k) of number of digraphs with a quasi-source on n labeled nodes and with k arcs, k=0,1,..,n*(n-1). %H A057272 V. Jovovic and G. Kilibarda, <a href="http://dx.doi.org/10.1016/S0012-365X(00)00112-6">Enumeration of labeled quasi-initially connected digraphs</a>, Discrete Math., 224 (2000), 151-163. %e A057272 Triangle starts: %e A057272 1; %e A057272 0,2,1; %e A057272 0,0,12,20,15,6,1; %e A057272 0,0,0,104,426,768,920,792,495,220,66,12,1; %e A057272 ... %e A057272 Number of digraphs with a quasi-source on 3 labeled nodes is 54=12+20+15+6+1. %Y A057272 Row sums give A049414. Cf. A057270, A057271, A057273-A057279. %K A057272 nonn,tabf %O A057272 1,3 %A A057272 _Vladeta Jovovic_, Goran Kilibarda, Sep 14 2000