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 A383662 #16 Jun 23 2025 14:41:10 %S A383662 6,0,2,302,8,151,19072,9862,18202,1603948,1067638,1310791,107096187, %T A383662 55488142,66608924,6149236417,3374967940,4259963914,402706752421, %U A383662 239187240144,292999006211,26470682075988,15360134570696,18595568012716,1685811256230132,964730606632516,1173328484648288 %N A383662 Number of closed knight's tours in the first 2n cells of a 6 X ceiling(2n/6) board. %C A383662 If n is not a multiple of 3, the rightmost column has only 2n mod 6 rows (see example). %D A383662 Donald E. Knuth, Hamiltonian paths and cycles, Prefascicle 8a of The Art of Computer Programming (work in progress, 2025). %H A383662 Don Knuth, <a href="/A383662/b383662.txt">Table of n, a(n) for n = 11..150</a> %H A383662 Don Knuth, <a href="https://cs.stanford.edu/~knuth/programs/dynaham.w">CWEB program</a> with input parameter board,50,6,0,0,5,0,0.gb [the graph "board(50, 6, 0, 0, 5, 0, 0)" generated by the Stanford GraphBase]. %F A383662 a(3n) = A175881(n). %e A383662 For n=11, one of the a(11)=6 solutions is %e A383662 1 4 13 16 %e A383662 12 15 2 5 %e A383662 3 22 17 14 %e A383662 8 11 6 19 %e A383662 21 18 9 %e A383662 10 7 20 . %Y A383662 Cf. A175881, A383660, A383661, A383663, A383664. %K A383662 nonn %O A383662 11,1 %A A383662 _Don Knuth_, May 04 2025