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 A137975 #9 Oct 22 2019 19:23:49
%S A137975 1,2,8,32,167,928,5924,40211,293370,2255406,18201706,153176115,
%T A137975 1339271815,12124484941,113362749476,1092329626380,10827837622018,
%U A137975 110249198676581,1151562885666429,12324860339781102,135026515460855978,1512882677086123938,17321462912397361409,202503301170606347695,2415733704608822524946,29387239261415606708127
%N A137975 Row sums of A139621, number of connected directed multigraphs with loops and no vertex of degree 0, with n arcs.
%C A137975 Inverse Euler transform of A052171.
%H A137975 Andrew Howroyd, <a href="/A137975/b137975.txt">Table of n, a(n) for n = 0..50</a>
%o A137975 (PARI) \\ See A139621 for G, InvEulerMT.
%o A137975 seq(n)={vecsum([Vec(p+O(y^n), -n) | p<-InvEulerMT(vector(n, k, G(k, y + O(y^n))))])} \\ _Andrew Howroyd_, Oct 22 2019
%Y A137975 Row sums of A139621.
%Y A137975 Cf. A052171, A139627.
%K A137975 nonn
%O A137975 0,2
%A A137975 _Benoit Jubin_, May 01 2008, May 10 2008
%E A137975 Data corrected to match A052171. - _R. J. Mathar_, Jul 25 2017