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 A374827 #14 Jul 22 2024 09:49:58 %S A374827 1,2,9,28,150,636,3290,6192,35145,57380,230494,192588,1055535,1177148 %N A374827 Place n equally spaced points on the circumference of a circle of radius r and then connect each pair of points with straight lines whose intersections create A007569(n) - n additional points. Draw a circle of radius r around each of the A007569(n) points. The sequence gives the total number of curved edges formed from all circle intersections. %H A374827 Scott R. Shannon, <a href="/A374827/a374827.jpg">Image for n = 2</a>. In this and other images the starting circles' centers are shown as white dots. %H A374827 Scott R. Shannon, <a href="/A374827/a374827_1.jpg">Image for n = 3</a>. %H A374827 Scott R. Shannon, <a href="/A374827/a374827_2.jpg">Image for n = 4</a>. %F A374827 a(n) = A374825(n) + A374826(n) - 1, by Euler's formula. %Y A374827 Cf. A374825 (vertices), A374826 (regions), A374828 (k-gons), A007569 (total circles), A183207, A374339. %K A374827 nonn,more %O A374827 1,2 %A A374827 _Scott R. Shannon_, Jul 21 2024