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 A169775 #11 Jul 01 2017 23:00:00 %S A169775 2,0,0,0,8,0,16,0,48,0,200,0,616,0,1832,0,6008,0,19304,0,62180,0, %T A169775 189580,0,615792,0,1895952,0,6136708,0,18699436,0,60490008,0, %U A169775 184450888,0,595959276,0,1811054676,0,5847417040,0,17754996288,0,57292227492 %N A169775 Number of open knight's tour diagrams of a 3 X n chessboard that are symmetric under 180-degree rotation and have "type B": the endpoints occur in different columns and disagree in color with the cells in the nearest corner. %D A169775 D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010. %H A169775 George Jelliss, <a href="http://www.mayhematics.com/t/oa.htm">Open knight's tours of three-rank boards</a>, Knight's Tour Notes, note 3a (21 October 2000). %H A169775 George Jelliss, <a href="http://www.mayhematics.com/t/ob.htm">Closed knight's tours of three-rank boards</a>, Knight's Tour Notes, note 3b (21 October 2000). %H A169775 D. E. Knuth <a href="/A169770/a169770.txt">Generating functions for A169770-A169777 and A169696.</a> %F A169775 A169775(n)=0 unless n mod 2 = 0. %Y A169775 Cf. A070030, A169696, A169764-A169777. %K A169775 nonn %O A169775 4,1 %A A169775 _N. J. A. Sloane_, May 10 2010, based on a communication from _Don Knuth_, Apr 28 2010 %E A169775 a(31)-a(48) from _Andrew Howroyd_, Jul 01 2017