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 A364830 #17 Aug 12 2023 00:41:43 %S A364830 0,0,0,0,0,1,0,0,0,1,0,9,0,1,4,0,0,8,0,11,4,1,0,29,0,1,0,11,0,43,0,0, %T A364830 4,1,8,50,0,1,4,39,0,49,0,11,24,1,0,73,0,12,4,11,0,33,8,43,4,1,0,193, %U A364830 0,1,28,0,8,57,0,11,4,71,0,164,0,1,28,11,12,61 %N A364830 a(n) is the number of line intersections (not coinciding with a vertex) inside a regular n-gon after inscribing (always starting from the same point), for each proper divisor d_i of n greater than 1, a regular d_i-gon. %C A364830 Inspired by an X (or Twitter) post by Matt Henderson (see links section). %H A364830 Matt Henderson, <a href="https://twitter.com/matthen2/status/1639925895254224898">X post</a>, 2023. %H A364830 Paolo Xausa, <a href="/A364830/a364830.pdf">Illustration of first terms</a>. %H A364830 Paolo Xausa, <a href="/A364830/a364830_1.pdf">Illustration of a(60)</a>. %F A364830 a(n) = 0 if n is prime, a power of 2 or A032741(n) <= 2. %F A364830 a(n) = A364838(n) - n. %Y A364830 Cf. A006561, A007569, A032741, A364828, A364829, A364838. %K A364830 nonn %O A364830 1,12 %A A364830 _Paolo Xausa_, Aug 09 2023