Mathematicians Solve Minimum Sudoku Problem

This weekend it was announced that the so-called Sudoku problem had finally been solved. This was to prove that there exists no Sudoku grid with only 16 starting clues that would admit a unique solution. As reported in Technology Review, Gary McGuire and colleagues from University College Dublin have cracked the problem thanks to the magic of brute force: they used a really big computer for a whole year to solve all the possible grids with 16 starting clues-more than five billion of them-and check that indeed, none of them had a unique solution. This took more than seven million processor core-hours of computation. Now we're all waiting for a smart proof using only paper and pencil...