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 A359690 #14 Feb 16 2025 08:34:04 %S A359690 5,13,69,289,1971,3997,20371,45751,120957,205299,629847,897801, %T A359690 2334409,3461459,5517131,8468061 %N A359690 Number of vertices in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n. %C A359690 The number of vertices along each edge is A005728(n). No formula for a(n) is known. %H A359690 Scott R. Shannon, <a href="/A359690/a359690.png">Image for n = 1</a>. %H A359690 Scott R. Shannon, <a href="/A359690/a359690_1.png">Image for n = 2</a>. %H A359690 Scott R. Shannon, <a href="/A359690/a359690_2.png">Image for n = 3</a>. %H A359690 Scott R. Shannon, <a href="/A359690/a359690_3.png">Image for n = 4</a>. %H A359690 Scott R. Shannon, <a href="/A359690/a359690_4.png">Image for n = 5</a>. %H A359690 Scott R. Shannon, <a href="/A359690/a359690_5.png">Image for n = 6</a>. %H A359690 Scott R. Shannon, <a href="/A359690/a359690_6.png">Image for n = 7</a>. %H A359690 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CompleteBipartiteGraph.html">Complete Bipartite Graph</a>. %H A359690 Wikipedia, <a href="https://en.wikipedia.org/wiki/Farey_sequence">Farey sequence</a>. %F A359690 a(n) = A359693(n) - A359692(n) + 1 by Euler's formula. %Y A359690 Cf. A359691 (crossings), A359692 (regions), A359693 (edges), A359694 (k-gons), A005728, A331755, A359654, A358887, A358883, A006842, A006843. %K A359690 nonn,more %O A359690 1,1 %A A359690 _Scott R. Shannon_ and _N. J. A. Sloane_, Jan 11 2023