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 A333032 #13 Jun 01 2025 17:39:18 %S A333032 1,12,48,147,291,519,879,1383,2079,3039,4359,5991,7983,10515,13731, %T A333032 17571,22131,27543,33951,41271,49599,59355,70779,83499,97611,113763, %U A333032 132243,152619,175035,199707,226827,256443,288747,324603,364395,407139,452979,503319 %N A333032 Number of triangular regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition). %C A333032 See A328526 for images of the triangular frame. %H A333032 Lars Blomberg, <a href="/A333032/b333032.txt">Table of n, a(n) for n = 1..65</a> %Y A333032 Cf. A328526 (regions), A333030 (edges), A333031 (vertices), A333033 (4-gons), A331776 (square frame), A274586 (filled triangle). %K A333032 nonn %O A333032 1,2 %A A333032 _Scott R. Shannon_ and _N. J. A. Sloane_, Mar 05 2020 %E A333032 a(12) and beyond from _Lars Blomberg_, May 01 2020