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 A341269 #35 Oct 07 2021 16:23:05 %S A341269 1,2,20,548,40440,8442742,5088482972,8963926817126,46591697187961736 %N A341269 Number of non-extendable self-avoiding walks in an n X n grid starting at the top left corner. %C A341269 A self-avoiding walk is non-extendable if it ends on a square which has all its neighbors already visited. Not all paths are Hamiltonian. See examples. %C A341269 All paths that start by moving one square to the right are symmetrical with all paths that start by moving one square down. This symmetry results in a(n) divisible by 2 for n > 1. %e A341269 Example of a self-avoiding walk on a 3 X 3 grid that visits every node (Hamiltonian path): %e A341269 . %e A341269 1---2---3 %e A341269 | %e A341269 6---5---4 %e A341269 | %e A341269 7---8---9 %e A341269 . %e A341269 Two examples of a self-avoiding walk on a 3 X 3 grid that do not visit every node: %e A341269 . %e A341269 1---2 7 %e A341269 | | %e A341269 X 3 6 %e A341269 | | %e A341269 X 4---5 %e A341269 . %e A341269 or %e A341269 . %e A341269 1 8---7 %e A341269 | | %e A341269 2---3 6 %e A341269 | | %e A341269 X 4---5 %e A341269 . %Y A341269 Cf. A145157 (Hamiltonian case). %K A341269 nonn,walk,more %O A341269 1,2 %A A341269 _Ryan Bresler_, Feb 07 2021 %E A341269 a(8)-a(9) from _Andrew Howroyd_, Feb 08 2021 %E A341269 a(6) corrected by _Henry Bottomley_, Oct 07 2021