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 A126066 #10 Apr 20 2020 00:26:46 %S A126066 1,1,1,1,1,1,1,3,3,3,1,1,1,1,4,9,18,24,30,24,18,9,4,1,1,1,1,4,11,38, %T A126066 89,210,382,616,787,880,787,616,382,210,89,38,11,4,1,1,1,1,4,12,48, %U A126066 165,567,1703,4623,10836,22273,39866,62650,86209,104456,111256,104456,86209,62650,39866,22273,10836,4623,1703,567,165,48,12,4,1,1 %N A126066 Triangle read by rows: T(n,k) is the number of unlabeled digraphs on n nodes with k arcs up to reversing the arcs, k=0..n*(n-1). %H A126066 Andrew Howroyd, <a href="/A126066/b126066.txt">Table of n, a(n) for n = 0..2680</a> (rows 0..20) %F A126066 T(n,k) = (A052283(n,k) + A126066(n,k))/2. - _Andrew Howroyd_, Apr 20 2020 %e A126066 Triangle begins: %e A126066 1; %e A126066 1; %e A126066 1,1,1; %e A126066 1,1,3,3,3,1,1; %e A126066 1,1,4,9,18,24,30,24,18,9,4,1,1; %e A126066 ... %e A126066 G.f. for fourth row is obtained if we set x(i) = 1+x^i, i=1..12 in (1/48)*(x(1)^12+12*x(1)^2*x(2)^5+4*x(2)^6+8*x(3)^4+12*x(4)^3+3*x(1)^4*x(2)^4+8*x(6)^2) %Y A126066 Row sums give A054933. %Y A126066 Cf. A052283, A126066. %K A126066 nonn,tabf %O A126066 0,8 %A A126066 _Vladeta Jovovic_, Feb 28 2007 %E A126066 a(0)=1 prepended and terms a(64) and beyond from _Andrew Howroyd_, Apr 20 2020