Solving the Sudoku: Magic number turns out to be 17

(CBS News) 

Puzzled by the secret of the Sudoku? You're not alone; millions of people have tried their hand at the mathematical problem-solving game since it was first popularized in 1986 in Japan. The challenge is to fill in a 9X9 grid of squares where certain cells already contain digits numbering between 1 and 9.

The idea is to fill in the remaining cells so that the rows and columns - as well as each 3×3 box - all contains all the digits numbering between 1 and 9 exactly one time.

Now Gary McGuire, a mathematician at University College Dublin, has come up with what he says is a proof that finds the minimum number of clues, or starting digits, needed to complete the game is 17. That's been a long-held assumption for quite some time. So why haven't mere mortals been able to confirm that believe? Of course, McGuire had help in the form of a supercomputer to help him in his work.

McGuire and his colleagues lay out their findings in this article they published in the online publication arXiv:1201.0749v1. You can also read a good write-up at Nature.com