Question: How many nails can be hammered into the chessboard with Maple?

A more serious formulation is the following. Let us consider the cartesian product
 {1, 2, 3, 4, 5, 6, 7, 8} x {1, 2, 3, 4, 5, 6, 7, 8} as a subset of the plane xOy. What is its maximal subset which does not include three points belonging to a straight line? How to find this with Maple? I don't know the answer. My hypothesis is the number of the elements of that set is about 10.

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