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 A333030 #9 May 02 2020 03:21:30 %S A333030 3,21,132,432,951,1800,3069,4956,7569,11040,15585,21492,28971,38328, %T A333030 49527,62922,79113,98358,120939,147486,177873,212358,251823,296898, %U A333030 347709,404772,468189,538680,617439,704742,801039,907842,1024629,1151544,1289319,1438686 %N A333030 Number of edges in an equilateral triangle "frame" of size n (see Comments in A328526 for definition). %C A333030 For n<=3 the terms equal A274586(n). See A328526 for images of the triangular frame. %H A333030 Lars Blomberg, <a href="/A333030/b333030.txt">Table of n, a(n) for n = 1..65</a> %Y A333030 Cf. A328526 (regions), A333031 (vertices), A331776 (square frame), A274586 (filled triangle). %K A333030 nonn %O A333030 1,1 %A A333030 _Scott R. Shannon_ and _N. J. A. Sloane_, Mar 05 2020 %E A333030 a(12) and beyond from _Lars Blomberg_, May 01 2020