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 A331906 #20 Feb 16 2025 08:33:59 %S A331906 40,1100,7330,25540,65930,136200,263010,458410,740550,1142740,1681640, %T A331906 2400970,3338850,4495510,5962220,7736150,9924580,12442880,15527670, %U A331906 19132140,23301600,28070620,33585800,39919140,47157510,55209750,64185300,74311940,85731780,98167130 %N A331906 The number of regions inside a pentagram formed by the straight line segments mutually connecting all vertices and all points that divide the sides into n equal parts. %C A331906 The terms are from numeric computation - no formula for a(n) is currently known. %H A331906 Scott R. Shannon, <a href="/A331906/a331906.png">Pentagram regions for n = 1</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_1.png">Pentagram regions for n = 2</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_2.png">Pentagram regions for n = 3</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_3.png">Pentagram regions for n = 4</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_4.png">Pentagram regions for n = 5</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_5.png">Pentagram regions for n = 6</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_6.png">Pentagram regions with random distance-based coloring for n = 1</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_7.png">Pentagram regions with random distance-based coloring for n = 2</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_8.png">Pentagram regions with random distance-based coloring for n = 3</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_9.png">Pentagram regions with random distance-based coloring for n = 4</a>. %H A331906 Scott R. Shannon, <a href="/A331906/a331906_10.png">Pentagram regions with random distance-based coloring for n = 5</a>. %H A331906 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Pentagram.html">Pentagram</a>. %Y A331906 Cf. A331907 (n-gons), A333117 (vertices), A333118 (edges), A007678, A092867, A331452. %K A331906 nonn %O A331906 1,1 %A A331906 _Scott R. Shannon_ and _N. J. A. Sloane_, Jan 31 2020 %E A331906 a(7)-a(30) from _Lars Blomberg_, May 06 2020