OFFSET
0,3
COMMENTS
10 <= a(7) <= 12, 11 <= a(8) <= 13, 12 <= a(9) <= 15, 13 <= a(10) <= 17.
LINKS
Math.StackExchange, A largest subset of a cubic lattice with unique distances between its points, Aug 03 2016.
Ed Pegg Jr, No Repeated Distances, Wolfram Demonstrations Project, May 03 2013.
A. Zimmermann. Al Zimmermann's Programming Contests: Point Packing, Oct 10 2009.
EXAMPLE
For n = 5, a(5) >= 7 is witnessed by {(1,1,1), (1,1,2), (1,1,4), (1,2,5), (2,3,1), (4,4,5), (5,5,4)}. There are 4223 distinct (up to rotation and reflection) 7-point configurations without repeated distances, and none of them can be extended to 8 points, so a(5) = 7.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Vladimir Reshetnikov, Aug 04 2016
STATUS
approved