OFFSET
1,2
COMMENTS
Symmetric tours are only possible on boards of odd length. The only symmetry is a rotation by 180 degrees which results in the reversal of the tour.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..250
George Jellis, Knight's tours of Four Rank Boards
EXAMPLE
a(2) = 2 because there are 2 symmetric 4 X 3 tours:
+----+----+----+----+ +----+----+----+----+
| 8 | 11 | 6 | 3 | | 1 | 4 | 7 | 10 |
+----+----+----+----+ +----+----+----+----+
| 1 | 4 | 9 | 12 | | 8 | 11 | 2 | 5 |
+----+----+----+----+ +----+----+----+----+
| 10 | 7 | 2 | 5 | | 3 | 6 | 9 | 12 |
+----+----+----+----+ +----+----+----+----+
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Oct 12 2019
STATUS
approved