PlaySudoku.us
Hard · Puzzle #415
3
9
8
4
4
1
5
7
3
5
6
1
4
4
3
7
2
9
9
6
5
8
7
2
5
4
The hardest Sudoku puzzles require techniques equivalent to propositional logic — the same foundation used in computer proofs.
The hardest Sudoku puzzles require techniques equivalent to propositional logic — the same foundation used in computer proofs.
The hardest Sudoku puzzles require techniques equivalent to propositional logic — the same foundation used in computer proofs.
The hardest Sudoku puzzles require techniques equivalent to propositional logic — the same foundation used in computer proofs.