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 A372731 #9 May 12 2024 10:04:50 %S A372731 6,51,301,1272,3285,8401,16050,30036,49801,80916,120447,180307,249108, %T A372731 350145,465898,618213 %N A372731 Number of vertices among all distinct circles that can be constructed from the 3 vertices and the equally spaced 3*n points placed on the sides of an equilateral triangle when every pair of the 3 + 3*n points are connected by a circle and where the points lie at the ends of the circle's diameter. %C A372731 A circle is constructed for every pair of the 3 + 3*n points, the two points lying at the ends of a diameter of the circle. %H A372731 Scott R. Shannon, <a href="/A372731/a372731.jpg">Image for n = 0</a>. In this and other images the 3 + 3*n vertices forming the triangle are drawn larger for clarity. %H A372731 Scott R. Shannon, <a href="/A372731/a372731_1.jpg">Image for n = 1</a>. %H A372731 Scott R. Shannon, <a href="/A372731/a372731_2.jpg">Image for n = 2</a>. %H A372731 Scott R. Shannon, <a href="/A372731/a372731_3.jpg">Image for n = 3</a>. %H A372731 Scott R. Shannon, <a href="/A372731/a372731_4.jpg">Image for n = 4</a>. %F A372731 a(n) = A372733(n) - A372732(n) + 1 by Euler's formula. %Y A372731 Cf. A372732 (regions), A372733 (edges), A372734 (k-gons), A372735 (number of circles), A372614, A371373, A354605, A360351. %K A372731 nonn,more %O A372731 0,1 %A A372731 _Scott R. Shannon_, May 12 2024