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 A307891 #12 Sep 29 2019 07:05:56 %S A307891 0,0,0,0,0,0,0,1,0,2,2,3,4,9,6,15,14,21,22,37,30,53,52,69,74,102,96 %N A307891 Rectilinear crossing number A014540(n) - crossing number A000241(n) of complete graph on n nodes. %e A307891 For 8 nodes the crossing number is 18 and the rectilinear crossing number is 19. The difference for 8 nodes is 1. Thus a(8)=1. %Y A307891 Cf. A000241, A014540, A028723. %K A307891 nonn,hard,more %O A307891 1,10 %A A307891 _Ed Pegg Jr_, May 03 2019