Ken's Puzzle of the Week

Unique 3x3 Grids


   In an 8x8 grid of squares, blacken as few unit squares as possible to make each 3x3 grid of nine squares unique (There are 36 3x3 grids.)  For example, in a 5x5 grid of squares, you need to make only one square black.

Repeat for 6x6 thru 10x10 grids of squares.

Source: Original.
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