udosuk wrote:A sudoku grid where no digits are diagonally adjacent, and "knightly" adjacent... I've tried to make grids that each digit cannot have a duplicate in its 5x5 neighbourhood, and it's easy to prove the impossibility...
Checked the 5x5 and can confirm its impossible. The only thing I can add is my computer found only 2 templates that even meet the 5x5 requirement. This one:
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and its reflection. As you need 9 non-overlapping templates to make a sudoku it is clearly impossible.
