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 A215620 #24 Feb 16 2025 08:33:18 %S A215620 1,2,4,11,34,155,1026,11666,226916,6810525 %N A215620 Numbers of apex graphs (graphs which become or remain planar upon the removal of a single vertex) on n vertices. %C A215620 Trivially includes planar graphs. %H A215620 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ApexGraph.html">Apex Graph</a> %Y A215620 Cf. A215621 (nonplanar apex graphs). %Y A215620 Cf. A076317 (number of 5-colorable simple graphs on n nodes). %K A215620 nonn,more %O A215620 1,2 %A A215620 _Eric W. Weisstein_, Aug 17 2012 %E A215620 a(10) from _Eric W. Weisstein_, Aug 20 2012