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 A126750 #21 May 31 2018 05:11:10 %S A126750 0,0,0,1,1,5,8,42,146,956,6643,65921,818448,13442572,287665498, %T A126750 8099980771,300760170216,14791653463768,967055338887805, %U A126750 84368806391412395,9855854129239183783,1546801291978378704267 %N A126750 Number of 2-connected (or biconnected) graphs on n nodes with chromatic number 2. %C A126750 Equally, number of 2-connected (or biconnected) bipartite graphs on n nodes. %C A126750 Also number of biconnected triangle-free graphs on n nodes with chromatic number 2, since chromatic number 2 implies triangle-free. - _Gordon Royle_, Apr 11 2007 %C A126750 See the Gainer-Dewar/Gessel reference for formulas and Sage code. - _Ralf Stephan_, May 18 2013 %H A126750 Keith M. Briggs, <a href="http://keithbriggs.info/cgt.html">Combinatorial Graph Theory</a> %H A126750 C. J. Colbourn and C. Huybrechts, <a href="https://doi.org/10.1016/j.disc.2007.09.039">Fully gated graphs,: recognition and convex operations</a>, Discrete Math., 308 (2008), 5184-5195. %H A126750 A. Gainer-Dewar and I. M. Gessel, <a href="https://arxiv.org/abs/1304.0139">Enumeration of bipartite graphs and bipartite blocks</a>, arXiv:1304.0139 [math.CO], 2013-2014. %Y A126750 A diagonal of triangle in A126749. %K A126750 nonn %O A126750 1,6 %A A126750 _N. J. A. Sloane_, Feb 18 2007, Oct 01 2008