John, I was going to say it's easy - he's memorised x to the power n for all positive integers x and n - but that would be harder than doing the calculations. Is it a trick? Hugh. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.bcn.mythic-beasts.com/pipermail/bitlist/attachments/20130618/450a1d2e/attachment.htm