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 A351109 #7 Feb 04 2022 14:40:42 %S A351109 1,0,2,8,40,1380,211164,205331148 %N A351109 Number of simple paths for a Racetrack car (using von Neumann neighborhood) with initial velocity zero, going from one corner to the diagonally opposite corner on an n X n grid. %H A351109 Wikipedia, <a href="https://en.wikipedia.org/wiki/Racetrack_(game)">Racetrack</a> %e A351109 For n = 4 the following paths, together with their reflections in the diagonal, exist. The numbers give the positions of the car after successive steps. In total, there are a(4) = 2*4 = 8 possible paths. %e A351109 ...3 ...4 ...4 ...5 %e A351109 .... ...3 ..3. ...4 %e A351109 ..2. ..2. ..2. ...3 %e A351109 01.. 01.. 01.. 012. %Y A351109 Main diagonal of A351108. %Y A351109 Cf. A007764, A351042, A351107. %K A351109 nonn,more %O A351109 1,3 %A A351109 _Pontus von Brömssen_, Feb 01 2022