"Peter T" wrote:
I knocked something up to get a feel, pretty crude
and slow but it churned out 1,947,792 combinations
of 6 numbers of which 16,431 fitted your '4 out of 6' criteria.

I would like to understand why you and I got very different results.

Please upload your results -- the 16,431 combinations -- to a file-sharing
website and post the "shared", "public" or "view-only" link (aka URL;
http://...) in a response here. The following is a list of some free
file-sharing websites; or use your own.

Box.Net: http://www.box.net/files
Windows Live Skydrive: http://skydrive.live.com
MediaFi http://www.mediafire.com
FileFactory: http://www.filefactory.com
FileSavr: http://www.filesavr.com
FileDropper: http://www.filedropper.com
RapidSha http://www.rapidshare.com