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 A169777 #10 Mar 03 2016 09:46:01 %S A169777 3,0,0,14,104,146,773,2698,14350,32296,161714,460022,2159794,5851548, %T A169777 26468357,76442996,330719293,965759972,4056479056,12186078360, %U A169777 49668414086,151760518296,604396415979,1879966906486,7330203447133,23126786408904,88609897281582 %N A169777 Number of geometrically distinct open knight's tours of a 3 X n chessboard. %D A169777 D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010. %H A169777 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 A169777 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 A169777 D. E. Knuth <a href="/A169770/a169770.txt">Generating functions for A169770-A169777 and A169696.</a> %F A169777 a(n) = A169696(n)/4 + A169776(n)/2. %e A169777 The three distinct 3x4 tours were published by Euler in Memoires Acad. Roy. Sci. (Berlin, 1759), 310-337. %Y A169777 Cf. A070030, A169696, A169764-A169777. %K A169777 nonn %O A169777 4,1 %A A169777 _N. J. A. Sloane_, May 10 2010, based on a communication from _Don Knuth_, Apr 28 2010