Flammenkamp's work on the no-3-in-line problem is summarized in this table: http://wwwhomes.uni-bielefeld.de/achim/no3in/table.txt The only known examples of a fully-symmetric (8 symmetries) set of 2N points on NxN grid, no 3 in line, have (says Flammenkamp) N=2, N=4, and N=10 and each is unique. The N=2 set is, of course, the full 2x2 grid. The N=4 set is the "o"s pictured below: xoox oxxo oxxo xoox and can be regarded as the (x,y) with x*y mod 5=+-2, using the grid with coordinates {1,2,3,4}. I discovered the N=10 set has a nice description: It is the set of (x,y) with x*y mod 11 = +-5. In case you are hoping you can substitute other values for 5 and 11 to get more lovelies, well, I already tried that. Nothing for a long way. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)