In fact it is a known conjecture that for every n there is a solution. Random methods suggest this. So I think here "a(6) has no solution less than 700000" is good. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://list.seqfan.eu/pipermail/seqfan/attachments/20070610/f5dbd9cf/attachment-0001.htm>