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 A200893 #11 May 04 2021 14:33:43 %S A200893 1,0,1,0,1,0,0,1,1,4,0,1,1,14,42,0,1,3,63,843,9050,0,1,3,224,7506, %T A200893 342743,6965359,0,1,8,1022,71542,6971973 %N A200893 Triangle read by rows: number of meanders filling out an n X k grid. %C A200893 The sequence counts the distinct closed paths that visit every cell of an n-by-k rectangular lattice at least once, that never cross any edge between adjacent squares more than once, and that do not self-intersect. Paths related by rotation and/or reflection of the square lattice are not considered distinct. %H A200893 Jon Wild, <a href="/A200893/a200893.png">Illustration for T(5,4) = 14</a> %H A200893 Jon Wild, <a href="/A200893/a200893_1.png">Illustration for T(6,4)=63</a> %H A200893 Jon Wild, <a href="/A200893/a200893_2.png">Illustration for T(7,4)=224</a> %F A200893 T(n,3) appears to be equal to A090597. %e A200893 The 14 solutions for (n,k)=(5,4), 63 solutions for (n,k)=(6,4) and 224 solutions for (n,k)=(7,4) are illustrated in the supporting png files. %Y A200893 Cf. A200000 (sequence of entries for square grid). %K A200893 nonn,tabl %O A200893 1,10 %A A200893 _Jon Wild_, Nov 23 2011