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 A304124 #11 May 08 2018 03:56:28 %S A304124 1,2,4,10,29,120,685,6431,103164,2894632,138892304,11118977705, %T A304124 1459412127955 %N A304124 Number of simple graphs with n vertices which contain no K4 subgraph. %C A304124 The graphs do not need to be connected. %F A304124 a(n) = 1+A052450(n)+A052451(n). %Y A304124 Cf. A000088, A006785 (no K3), A115196 (graphs by clique number), A304125 (no K5). %K A304124 nonn,more %O A304124 1,2 %A A304124 _Brendan McKay_, May 06 2018 %E A304124 a(13) from _Brendan McKay_, May 08 2018