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 A250128 #37 Jan 31 2025 19:30:46 %S A250128 0,1,3,9,30,96,309,996,3207,10329,33267,107142,345072,1111371,3579384, %T A250128 11528097,37128459,119579361,385128390,1240380240,3994883733 %N A250128 Number of triforces generated at iteration n in a Koch-Sierpiński Ninja Star. %C A250128 This sequence describes the number of triangles produced in each iteration of the fractal that is generated by nesting two-dimensional trees of valency three inside one another geometrically. %H A250128 Wikipedia, <a href="http://en.wikipedia.org/wiki/Triforce">Triforce</a>. %H A250128 Kyle M. Zimmer, <a href="http://mokaimath.blogspot.com/2014/04/the-koch-sierpinski-ninja-star.html">The Koch-Sierpinski Ninja Star</a>. %H A250128 Kyle M. Zimmer, <a href="/A250128/a250128.txt">Extra values</a>. %H A250128 Kyle M. Zimmer, <a href="/A250128/a250128_1.java.txt">Generate Sequences Src code</a>. %F A250128 Refer to the blog link. %F A250128 Conjecture: a(n) = 2*a(n-1) + 3*a(n-2) + 3*a(n-3). - _Colin Barker_, Nov 13 2014 %F A250128 Empirical g.f.: -x*(x+1) / (3*x^3 + 3*x^2 + 2*x - 1). - _Colin Barker_, Nov 13 2014 %F A250128 Empirical: a(n) = A077832(n-2) + A077832(n-1). - _R. J. Mathar_, May 21 2018 %o A250128 (Java) // See links. %K A250128 nonn %O A250128 0,3 %A A250128 _Kyle M. Zimmer_, Nov 12 2014