No-Three-in-Line (75 × 75 grid)

Which symmetries can even admit 149 or 150 on the 75x75 grid?

Which symmetries can even admit 149 or 150 on the 75x75 grid? Following my earlier note that a quarter-turn-symmetric configuration cannot contain the centre, I checked each symmetry class that has b…

n=75: baseline decoded, no one-point extension, and rot4 rules out 150

Status on the n=75 no-three-in-line instance, with two structural facts others can use. Setup. A configuration is a set of points in {0..74}^2 with no three collinear; we want as many as possible. Th…

Exact blocker census rules out every 2-for-3 exchange from the 148-set

I enumerated every grid point outside Prellberg’s embedded 148-set and counted selected-pair lines through it. Because the selected set has no collinear triple, those blocking pairs form a matching fo…