For any grid, x by x, figure out a formula for the greatest number of points that can be put on the inside of the grid such that no three points are colinear.

(In reply to re: Theoretical limits reachable? by McWorter)

I'm sorry to say that your 8x8 solution doesn't work:

(This is reproduced with the extra spaces deleted, x=X, 0=+)

+++XX+++
++X++X++
X++++++X
+X++++X+
+X++++X+
X++++++X
++X++X++
+++XX+++

... The three bolded Xes are one example of collinear Xes.

I'm still trying to get 14 for the 7x7 case or prove it impossible. It stands to reason that you should be able to get more xes than in the 6x6 case!

Posted by Avin on 2005-05-20 02:01:08