A362027 Squares visited by a knight moving on a square-spiral numbered board where the knight moves to a previously unvisited square with a number as close as possible to the number of the current square. If two such squares exist the smaller numbered square is chosen.

1, 10, 3, 6, 9, 12, 15, 18, 7, 4, 11, 8, 5, 2, 13, 28, 25, 46, 21, 40, 17, 34, 59, 56, 29, 32, 55, 58, 33, 30, 53, 26, 47, 22, 19, 16, 37, 62, 95, 136, 91, 130, 87, 52, 49, 24, 27, 48, 51, 80, 83, 120, 123, 84, 81, 118, 77, 44, 41, 68, 103, 100, 63, 66, 39, 36, 61, 94, 57, 88, 127, 174, 229, 170

Offset

1,2

Comments

This sequence is finite: after 130 squares have been visited the square with number 50 is reached after which all eight neighboring squares the knight could move to have already been visited. See the linked image. The largest visited square is a(117) = 247 while the smallest unvisited square is 20.

Links

Scott R. Shannon, Table of n, a(n) for n = 1..130.

Scott R. Shannon, Image showing the 129 steps of the knight's path. The first and last squares are highlighted in green and red respectively while the eight squares blocking the final square are surrounded in blue.

Example

The board is numbered with the square spiral:
.
  17--16--15--14--13   .
   |               |   .
  18   5---4---3  12   29
   |   |       |   |   |
  19   6   1---2  11   28
   |   |           |   |
  20   7---8---9--10   27
   |                   |
  21--22--23--24--25--26
.
a(6) = 12 as after the knight moves to the square containing 9 the available unvisited squares are 4, 12, 22, 26, 28, 46, 48. Of these 12, where |12 - 9| = 3, is the closest number to 9. This is the first term to differ from A316667.

Crossrefs

Cf. A316667, A358278, A358150, A328929, A328909, A174344, A274923.

Sequence in context: A377015 A336208 A330189 * A358150 A335214 A338288

Adjacent sequences: A362024 A362025 A362026 * A362028 A362029 A362030

Keyword

nonn,fini,full

Author

Scott R. Shannon, Apr 05 2023

Status

approved