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 A359693 #9 Feb 16 2025 08:34:04 %S A359693 6,24,162,670,4456,8942,44470,98902,259114,438552,1330566,1897164, %T A359693 4893752,7246502,11544278,17678880 %N A359693 Number of edges in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n. %C A359693 The number of vertices along each edge is A005728(n). No formula for a(n) is known. %C A359693 See A359690 and A359692 for images of the graph. %H A359693 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CompleteBipartiteGraph.html">Complete Bipartite Graph</a>. %H A359693 Wikipedia, <a href="https://en.wikipedia.org/wiki/Farey_sequence">Farey sequence</a>. %F A359693 a(n) = A359690(n) + A359692(n) - 2*A005728(n) + 1 by Euler's formula. %Y A359693 Cf. A359690 (vertices), A359691 (crossings), A359692 (regions), A359694 (k-gons), A005728, A290132, A359655, A358888, A358884, A006842, A006843. %K A359693 nonn,more %O A359693 1,1 %A A359693 _Scott R. Shannon_ and _N. J. A. Sloane_, Jan 11 2023