How Many Latin Squares Are There? Counting Puzzle Grids
Latin squares go from 12 of order 3 to a 37-digit count at order 10. How the counts were found, how larger ones are estimated, and how grid loops are counted.
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Articles about loop puzzles
How to Solve Loop Puzzles: The Inside and Outside Method
Draw one closed loop by the numbers. Label cells inside or outside, use zeros, corners and the dot rule, then try a worked and a practice puzzle.