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 A304125 #10 May 08 2018 03:56:21 %S A304125 1,2,4,11,33,150,986,11416,245440,10164119,793907916,114150623175, %T A304125 29709609171994 %N A304125 Number of simple graphs with n vertices which contain no K5 subgraph. %C A304125 The graphs do not need to be connected. %F A304125 a(n) = 1+A052450(n)+A052451(n)+A052452(n). %Y A304125 Cf. A000088, A006785 (no K3), A115196 (graphs by clique number), A304124 (no K4). %K A304125 nonn,more %O A304125 1,2 %A A304125 _Brendan McKay_, May 06 2018 %E A304125 a(13) from _Brendan McKay_, May 08 2018