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 A034186 #6 Aug 07 2020 00:57:02 %S A034186 1,3,21,47,227,499,2321,5087,23429,51263,235881,515691,2372511, %T A034186 5185609,23856215,52139887,239863701,524238555,2411688233,5270900439, %U A034186 24248031407,52995614649 %N A034186 Number of symmetric n X 4 crossword puzzle grids. %Y A034186 Cf. A001333, A034184-A034187. %K A034186 nonn %O A034186 1,2 %A A034186 _Erich Friedman_