A338289 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.

1, 12, 9, 4, 7, 18, 35, 14, 29, 32, 55, 28, 13, 34, 17, 40, 21, 46, 25, 50, 79, 26, 47, 76, 43, 70, 105, 148, 65, 98, 37, 62, 33, 30, 53, 84, 49, 52, 87, 56, 59, 92, 89, 58, 91, 130, 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

Offset: 1

Author

Andrew Smith, Oct 20 2020

Keywords

• nonn
• fini

Comments

Board is numbered with the square spiral:

17--16--15--14--13 .

| | .

18 5---4---3 12 .

| | | | .

19 6 1---2 11 .

| | | .

20 7---8---9--10 .

| .

21--22--23--24--25--26

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...

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.

The sequences generated by 4 knights and 8 knights also produce new sequences not yet in the OEIS.

Links

• N. J. A. Sloane and Brady Haran, The Trapped Knight, Numberphile video (2019)

Crossrefs

Cf. A338288, A338290.