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 A338288 #23 Oct 24 2020 07:04:55 %S A338288 1,10,3,6,15,2,5,8,11,24,27,48,23,20,39,16,19,22,41,44,71,74,45,42,69, %T A338288 38,6,66,99,36,61,94,31,54,85,124,51,80,83,120,123,168,81,118,77,114, %U A338288 73,108,151,68,103,64,67,102,143,146,195,100,141,96,137,60,93,90,129,86,125,172,121,166,117,162,113,110,153 %N A338288 Squares visited by the white knight when a white knight and a black knight are moving on a spirally numbered board, always to the lowest available unvisited square; white moves first. %C A338288 Board is numbered with the square spiral: %C A338288 17--16--15--14--13 . %C A338288 | | . %C A338288 18 5---4---3 12 . %C A338288 | | | | . %C A338288 19 6 1---2 11 . %C A338288 | | | . %C A338288 20 7---8---9--10 . %C A338288 | . %C A338288 21--22--23--24--25--26 %C A338288 Both knights start on square 1, white moves to the lowest unvisited square (10), black then moves to the lowest unvisited square (12) and so on... %C A338288 This sequence is finite, on the white knight's 3999th step, square 3606 is visited, after which there are no unvisited squares within one knight move. %C A338288 The sequences generated by 4 knights and 8 knights also produce new sequences not yet in the OEIS. %H A338288 N. J. A. Sloane and Brady Haran, <a href="https://www.youtube.com/watch?v=RGQe8waGJ4w">The Trapped Knight</a>, Numberphile video (2019). %Y A338288 Cf. A338289, A338290. %K A338288 nonn,fini %O A338288 1,2 %A A338288 _Andrew Smith_, Oct 20 2020