OFFSET
1,3
COMMENTS
A319476(n) <= a(n) <= n(n-1)/2.
LINKS
Giovanni Resta, Illustration of a(3)-a(14)
EXAMPLE
For n = 5 a placement of five rooks on a 5 X 5 board with a(5) = 8 distinct distances is:
+---+---+---+---+---+
5 | | * | | | |
+---+---+---+---+---+
4 | * | | | | |
+---+---+---+---+---+
3 | | | | | * |
+---+---+---+---+---+.
2 | | | * | | |
+---+---+---+---+---+
1 | | | | * | |
+---+---+---+---+---+
A B C D E
The distances between pairs of pieces are:
1) sqrt(2) (A4 to B5 and C2 to D1)
2) 2*sqrt(2) (A4 to C2)
3) 3*sqrt(2) (A4 to D1)
4) sqrt(17) (A4 to E3)
5) sqrt(10) (B5 to C2)
6) 2*sqrt(5) (B5 to D1)
7) sqrt(13) (B5 to E3)
8) sqrt(5) (C2 to E3 and D1 to E3)
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Peter Kagey, Oct 12 2018
EXTENSIONS
a(11)-a(14) from Giovanni Resta, Oct 17 2018
a(15) from Bert Dobbelaere, Jan 01 2019
STATUS
approved