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Ken's Puzzle of the Week

Unique 8x8 Paths

Put four black squares into an 8x8 grid, such that the remaining white
squares can be connected in only one way in a closed loop, visiting each
white square exactly once (moving only up, down, right, or left.) One example is
above; only one closed loop can connect all the white squares. How many
different arrangements of four squares can determine a unique path?

Source: Original extension of previous 5x5
puzzle. To compare solutions, rotate/reflect your grid to put each
black square as close to the top left as possible.

Solution

Mail to Ken