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 A123936 #8 Oct 13 2019 23:02:41 %S A123936 0,0,4,0,41,372,3189,15544,94844,606556,3341926,18243164,100641235, %T A123936 541792652,2853058729,14909615644,77215251362,395393899688, %U A123936 2007472847598,10120652405244,50668068245114,252048156500636,1246766824001246,6135236528242698,30045694433419662 %N A123936 a(n) = A079137(n)/2. %C A123936 Number of nonequivalent (or geometrically distinct) directed open knight's tours on a 4 X n chessboard up to rotation and reflection. See A328341 for the number of geometrically distinct undirected open knights's tours. - _Andrew Howroyd_, Oct 12 2019 %H A123936 Andrew Howroyd, <a href="/A123936/b123936.txt">Table of n, a(n) for n = 1..500</a> %Y A123936 Cf. A079137, A123935, A328341. %K A123936 nonn %O A123936 1,3 %A A123936 _N. J. A. Sloane_, Oct 30 2006 %E A123936 Terms a(22) and beyond from _Andrew Howroyd_, Oct 13 2019