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A321534
a(n) gives the number of configurations of non-attacking rooks up to symmetry on an n X n chessboard such that the number of distinct directions between the rooks is given by A321531(n).
0
1, 1, 1, 1, 2, 21, 11, 74, 89, 18
OFFSET
1,5
COMMENTS
Conjecture: a(n) = A321532(n)/8 for n >= 4.
EXAMPLE
For n = 5, the a(5) = 2 essentially different configurations of nonattacking rooks with the maximal number of directions between them are given by the following two chessboards:
+---+---+---+---+---+
5| X | | | | |
+---+---+---+---+---+
4| | | X | | |
+---+---+---+---+---+
3| | | | X | |
+---+---+---+---+---+
2| | | | | X |
+---+---+---+---+---+
1| | X | | | |
+---+---+---+---+---+
A B C D E
+---+---+---+---+---+
5| X | | | | |
+---+---+---+---+---+
4| | | | X | |
+---+---+---+---+---+
3| | | X | | |
+---+---+---+---+---+
2| | | | | X |
+---+---+---+---+---+
1| | X | | | |
+---+---+---+---+---+
A B C D E
CROSSREFS
Sequence in context: A298822 A072397 A077208 * A212483 A084313 A140268
KEYWORD
nonn,more
AUTHOR
Peter Kagey, Nov 12 2018
STATUS
approved