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 A335781 #10 Jun 24 2020 10:05:38 %S A335781 1,18,127,162,388,468,154,846,1288,1422,1945,2106,2827,1260,3700,3870, %T A335781 4798,4950,5995,6318,4879,7524,8830,9108,10387,10764,12331,8730,13933, %U A335781 14454,16147,16434,18325,18846,16363,20718,23077,23472,25516,26154,28486,23274 %N A335781 a(n) is the number of regions formed by n-secting the angles of a nonagon (enneagon). %H A335781 Lars Blomberg, <a href="/A335781/b335781.txt">Table of n, a(n) for n = 1..200</a> %H A335781 Lars Blomberg, <a href="/A335781/a335781.png">Illustration for n=3</a> %H A335781 Lars Blomberg, <a href="/A335781/a335781_1.png">Illustration for n=4</a> %H A335781 Lars Blomberg, <a href="/A335781/a335781_2.png">Illustration for n=13</a> %H A335781 Lars Blomberg, <a href="/A335781/a335781_3.png">Illustration for n=14</a> %Y A335781 Cf. A332421 (n-sected sides, not angles), A335782 (vertices), A335783 (edges), A335784 (ngons). %K A335781 nonn %O A335781 1,2 %A A335781 _Lars Blomberg_, Jun 24 2020