Let S be the subset of the Cartesian product

{0,1,2,3,4,5,6} × {0,1,2,3,4,5,6}

that is represented by the black pixels in the plot below.

Click on the pixels in the plot to toggle pixels between black and white thus change the set S.

6
5
4
3
2
1
0
0 1 2 3 4 5 6

The set represented by the black pixels in the plot is

S = { (2,3), (5,5),} ⊆ {0,1,2,3,4,5,6}×{0,1,2,3,4,5,6}