Howard,

I read on one of the puzzle sites that it takes a minimum of 17 starting numbers to be able to guarantee a single solution. That's not to say that showing 17 numbers will guarantee a single solution, just that anything less than 17 starting numbers guarantees multiple solutions.

HTH,
Chad

>I've come to this conclusion...but haven't got it programmed yet...you need to fill in a few (maybe 9 spaces) with numbers from 1 to 9 - then attempt to solve the puzzle programmatically. If you can find a solution, then it's simply a matter of removing all but about 15 or so of the numbers and let the user try to solve it. It is really a very difficult thing to program. I'm finding that there are many programs that have pre-programmed puzzles and just load a puzzle instead of generating a new one.
>
>Let me know if you come up with something - I'd be very interested in taking a look.