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 A175855 #14 May 05 2025 15:05:20 %S A175855 0,0,8,44202,13311268,4557702762,1495135512514,491857035772330, %T A175855 161514101568508400,53034853662012222798,17414154188157170439208, %U A175855 5717847862749642677204182,1877435447920358266870897874,616447390029326136628439042672,202407848349722353779265745190616,66459727085467788423206394162537418,21821760546806761707309514948565417796,7165079447164571822068029945303172129766,2352622444655438705806553391345493395131580,772473271844923268504474277422663237674924998 %N A175855 The number of closed Knight's tours on a 5 X 2n board. %H A175855 J. de Ruiter, <a href="http://www.math.leidenuniv.nl/~jruiter/CountingDominoCoveringsAndChessboardCycles.pdf">Counting Domino Coverings and Chessboard Cycles</a>, 2010. %F A175855 a(n) = A383661(5n). - _Don Knuth_, May 05 2025 %e A175855 The smallest 5 X 2n board admitting a closed Knight's tour is the 5 X 6, on which there are 8 such tours. %Y A175855 A070030 deals with 3 X 2n boards, A175881 deals with 6 X n boards. %Y A175855 Cf. A383661. %K A175855 nonn %O A175855 1,3 %A A175855 _Johan de Ruiter_, Dec 05 2010