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 A383661 #17 Jun 23 2025 14:41:06 %S A383661 1,0,1,30,0,148,8,78,9309,612,62749,44202,42049,2916485,147192, %T A383661 18284136,13311268,13008389,973107552,51147756,6190192748,4557702762, %U A383661 4311375354,316985255470,16552301184,2015267424300,1495135512514,1417634375316,104324890543686,5459334927260,663068761241948 %N A383661 Number of closed knight's tours in the first 2n cells of a 5 X ceiling(2n/5) board. %C A383661 If n is not a multiple of 5, the rightmost column has only 2n mod 5 rows (see example). %D A383661 Donald E. Knuth, Hamiltonian paths and cycles. Prefascicle 8a of The Art of Computer Programming (work in progress, 2025). %H A383661 Don Knuth, <a href="/A383661/b383661.txt">Table of n, a(n) for n = 9..150</a> %H A383661 Don Knuth, <a href="https://cs.stanford.edu/~knuth/programs/dynaham.w">CWEB program</a> with input parameter board,60,5,0,0,5,0,0.gb [the graph "board(50, 6, 0, 0, 5, 0, 0)" generated by the Stanford GraphBase]. %F A383661 a(5n) = A175855(n). %e A383661 For n=9 the a(9)=1 example is %e A383661 1 14 5 10 %e A383661 4 9 2 15 %e A383661 13 18 11 6 %e A383661 8 3 16 %e A383661 17 12 7 . %Y A383661 Cf. A175855, A383660, A383662, A383663, A383664. %K A383661 nonn %O A383661 9,4 %A A383661 _Don Knuth_, May 04 2025