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 A121021 #5 Feb 01 2023 07:16:34 %S A121021 0,0,0,0,0,1,1,5,3,3080,5679 %N A121021 Number of crossing-optimal drawings of the complete graph K_n. %C A121021 a(11) is at least 10^6. %D A121021 Shengjun Pan and R. Bruce Richter, in "The Crossing Number of K_11 is 100", submitted. %e A121021 a(5)=1 because all drawings of K_5 with only 1 crossing are isomorphic. %Y A121021 Cf. A000241. %K A121021 nonn,more %O A121021 0,8 %A A121021 _David Applegate_, Sep 08 2006