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%I #14 Oct 24 2020 07:04:49
%S 1,12,9,4,7,18,35,14,29,32,55,28,13,34,17,40,21,46,25,50,79,26,47,76,
%T 43,70,105,148,65,98,37,62,33,30,53,84,49,52,87,56,59,92,89,58,91,130,
%U 57,88,127,174,229,122,167,82,119,78,115,160,75,72,107,150,201,104,147,144,193,140,95,136,185,132,135,184,181
%N Squares visited by the black 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 Board is numbered with the square spiral:
%C 17--16--15--14--13 .
%C | | .
%C 18 5---4---3 12 .
%C | | | | .
%C 19 6 1---2 11 .
%C | | | .
%C 20 7---8---9--10 .
%C | .
%C 21--22--23--24--25--26
%C 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 This sequence is finite, on the black knight's 1879th step, square 4242 is visited, after which there are no unvisited squares within one knight move.
%C The sequences generated by 4 knights and 8 knights also produce new sequences not yet in the OEIS.
%H N. J. A. Sloane and Brady Haran, <a href="https://www.youtube.com/watch?v=RGQe8waGJ4w">The Trapped Knight</a>, Numberphile video (2019)
%Y Cf. A338288, A338290.
%K nonn,fini
%O 1,2
%A _Andrew Smith_, Oct 20 2020
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