No Repeated Distances
Pick lattice points so that all distances between two points are unique. What is the tightest packing of these points? This Demonstration shows the best known results, as given in .
The tightest packing problem was the subject of . Of the many participants, the winner was Hugo Pfoertner.
 A. Zimmermann. "Al Zimmermann's Programming Contests: Point Packing." (Oct 10, 2009) www.azspcs.net/Contest/PointPacking/FinalReport.