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 A233343 #10 Feb 07 2017 17:27:45 %S A233343 1,441,614581,1064557805,1949314526229,3619365754064658, %T A233343 6743148875847013949,12573396789552627635974, %U A233343 23449283563696481324707977,43734844458505039459034141789,81570040233489554572733439665568,152137050633841639720340771054558899 %N A233343 Number of tilings of a 7 X 3n rectangle using 7n trominoes of any shape. %H A233343 Alois P. Heinz, <a href="/A233343/b233343.txt">Table of n, a(n) for n = 0..300</a> %H A233343 Wikipedia, <a href="https://en.wikipedia.org/wiki/Tromino">Tromino</a> %Y A233343 Trisection of column k=7 of A233320. %K A233343 nonn %O A233343 0,2 %A A233343 _Alois P. Heinz_, Dec 07 2013