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 A374825 #15 Jul 22 2024 09:50:43 %S A374825 0,1,4,13,71,313,1625,3073,17443,28601,115094,95965,527463,587441 %N A374825 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 vertices formed from all circle intersections. %H A374825 Scott R. Shannon, <a href="/A374825/a374825.jpg">Image for n = 2</a>. In this and other images the starting circles' centers are shown as white dots. %H A374825 Scott R. Shannon, <a href="/A374825/a374825_1.jpg">Image for n = 3</a>. %H A374825 Scott R. Shannon, <a href="/A374825/a374825_2.jpg">Image for n = 4</a>. %H A374825 Scott R. Shannon, <a href="/A374825/a374825_3.jpg">Image for n = 5</a>. %H A374825 Scott R. Shannon, <a href="/A374825/a374825_4.jpg">Image for n = 6</a>. %H A374825 Scott R. Shannon, <a href="/A374825/a374825_5.jpg">Image for n = 9</a>. %F A374825 a(n) = A374827(n) - A374826(n) + 1, by Euler's formula. %Y A374825 Cf. A374826 (regions), A374827 (edges), A374828 (k-gons), A007569 (total circles), A370980, A374338. %K A374825 nonn,more %O A374825 1,3 %A A374825 _Scott R. Shannon_, Jul 21 2024