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 A283753 #28 Jan 28 2022 21:52:39
%S A283753 1,1,1,3,4,4,1,1,8,22,37,47,38,27,13,5,1,1,27,108,326,667,1127,1477,
%T A283753 1665,1489,1154,707,379,154,61,16,5,1,1,91,582,2432,7694,19646,42148,
%U A283753 77305,122953,170315,206982,220768,207301,171008,124110,78813,43862,21209,8951,3242,1043,288,76,17,5,1,1,350,3024,17314,74676,266364,808620,2144407
%N A283753 Irregular triangular array read by rows: T(n,k) is the number of non-isomorphic unlabeled weakly connected digraphs on n nodes and with k arcs.
%C A283753 The range for the subindex k is from n-1 to n(n-1).
%C A283753 Obtained from A054733 by removing leading zeros.
%D A283753 E. Palmer and F. Harary, Graphical Enumeration, Academic Press, 1973.
%H A283753 Marko R. Riedel, <a href="http://math.stackexchange.com/questions/2187019/">Number of distinct connected digraphs</a>
%H A283753 Marko Riedel, <a href="/A283753/a283753_1.maple.txt">Maple code for sequences A052283, A283753.</a>
%e A283753 First rows are:
%e A283753 1;
%e A283753 1, 1;
%e A283753 3, 4, 4, 1, 1;
%e A283753 8, 22, 37, 47, 38, 27, 13, 5, 1, 1;
%e A283753 27, 108, 326, 667, 1127, 1477, 1665, 1489, 1154, 707, 379, ...
%o A283753 (PARI) \\ See A054733 for G, InvEulerMTS.
%o A283753 row(n)={Vecrev(polcoef(InvEulerMTS(sum(i=0, n, G(i, y)*x^i, O(x*x^n))), n)/y^(n-1))}
%o A283753 { for(n=1, 6, print(row(n))) } \\ _Andrew Howroyd_, Jan 28 2022
%Y A283753 Cf. A000273, A000238, A003085, A052283.
%K A283753 nonn,tabf
%O A283753 1,4
%A A283753 _Marko Riedel_, Mar 15 2017