17×17 4-coloring with no monochromatic rectangles. ⇒
21 February 2012, early morning
This is a pretty interesting problem that I had not heard about before. Basically, can you colour a 17×17 grid so that any 4 points you pick that form a rectangle don’t all share the same colour.
This is a post from my link log: If you click the title of this post you will be taken the web page I am discussing.