# How many minimal-clue sudoku puzzles are there?

It is known that there are a minimum of 17 clues needed to create a proper sudoku puzzle.

For how many puzzles is 17 sufficient? From the history of the minimal proof, I gather that there are multiple puzzles for which 17 clues are enough for a unique solution. Is 17 enough to specify every proper sudoku puzzle? Just a class or a few classes of puzzles?

• What is a unique solution? Please give an example. – martijnn2008 May 16 '14 at 17:14
• @martijnn2008 A unique sudoku puzzle refers to one which has one and only one solution. I'll edit it to include the proper terms. – user20 May 16 '14 at 17:29
• @Emracool I though so too, but Kevin is using the term 'unique solution' wrong. And Is 17 enough to uniquely specify every sudoku? still doesnt make sense, because you now say with 17 clues you can make every sudoku solution you want. – martijnn2008 May 16 '14 at 17:30
• @martijnn2008 perhaps I phrased it (/ was thinking about it) backwards. What I'm really after is does every valid sudoku board have a 17-clue starting board that uniquely specifies that puzzle. – Kevin May 16 '14 at 17:31
• @Kevin The term you're looking for is "proper sudoku," which I've edited in for you. – user20 May 16 '14 at 17:31