PlaySudoku.us
Hard · Puzzle #613
3
1
7
3
5
6
3
4
3
1
2
9
6
8
5
6
1
9
8
5
9
1
7
5
4
1
4
1
3
9
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.