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 A351924 #19 Mar 03 2022 17:17:04 %S A351924 3,5,7,11,15,21,27,29,43,53,59,75,87,85,115,131,135,165,183,185,223, %T A351924 245,251,291,315,317,367,395,379,453,483,485,547,581,587,651,687,689, %U A351924 763,803,795,885,927,925,1015,1061,1067,1155,1203,1205,1303,1355,1359,1461,1515,1517,1627,1685,1659 %N A351924 The number of vertices on a diagonal of a regular 2n-gon when all its vertices are connected by lines and where the diagonal passes through the center of the 2n-gon. %C A351924 No formula for a(n) is currently known. %H A351924 Scott R. Shannon, <a href="/A351924/a351924_3.png">Image of the 6-gon</a>. %H A351924 Scott R. Shannon, <a href="/A351924/a351924.png">Image of the 10-gon</a>. %H A351924 Scott R. Shannon, <a href="/A351924/a351924_1.png">Image of the 18-gon</a>. %H A351924 Scott R. Shannon, <a href="/A351924/a351924_2.png">Image of the 30-gon</a>. %e A351924 a(3) = 5 as a diagonal of a 6-gon, when all its vertices are connected by lines and where the diagonal passes through the center of the 6-gon, has five vertices on it - the two outer vertices, the central vertex, and two more vertices formed by intersections of the central diagonal with other diagonals. See the linked image of the 6-gon. %Y A351924 Cf. A007569, A006561, A146212. %K A351924 nonn %O A351924 2,1 %A A351924 _Scott R. Shannon_, Feb 25 2022