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 A341878 #11 Mar 02 2021 11:33:09 %S A341878 2,5,19,65,203,429,963,1643,2929,4173,7179,9985,14747,19503,27043, %T A341878 34511,46011,57171,73339,87509,111219,132809,162459,190703,229419, %U A341878 266285,315041,361179,423067,480201,556451,627039,718923,805217,915091,1017379,1148595,1270569,1423907,1564359 %N A341878 The number of vertices on a vesica piscis formed by the straight line segments mutually connecting all vertices and all points that divide the sides into n equal parts. %C A341878 The terms are from numeric computation - no formula for a(n) is currently known. %H A341878 Scott R. Shannon, <a href="/A341878/a341878.png">Vertices for n = 4</a>. %H A341878 Scott R. Shannon, <a href="/A341878/a341878_1.png">Vertices for n = 5</a>. %H A341878 Scott R. Shannon, <a href="/A341878/a341878_2.png">Vertices for n = 10</a>. %H A341878 Scott R. Shannon, <a href="/A341878/a341878_3.png">Vertices for n = 15</a>. %H A341878 Scott R. Shannon, <a href="/A341878/a341878_4.png">Vertices for n = 16</a>. %H A341878 Wikipedia, <a href="https://en.wikipedia.org/wiki/Vesica_piscis">Vesica piscis</a>. %Y A341878 Cf. A341877 (regions), A342152 (edges), A342153 (n-gons), A007569, A092866, A340644, A340686. %K A341878 nonn %O A341878 1,1 %A A341878 _Scott R. Shannon_ and _N. J. A. Sloane_, Feb 22 2021