Thread: Head, meet wall
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Old 2007-02-27, 11:01   #4
(loop (#_fork))
fivemack's Avatar
Feb 2006
Cambridge, England

3·19·113 Posts

Originally Posted by akruppa View Post
So does the Aliquot sequence terminate with a prime? What was the starting value?
Nothing so exciting ... I pulled out factors less than 10^5 by trial division, then ran gmp-ecm (which doesn't by default check primality on its input) for a while, then ggnfs. The idea that a randomish 115-digit number might be prime hadn't crossed my mind, and if it had I'd have expected the tools to pick it up.

I've switched to running gmp-ecm on the full numbers ... it's not the efficient way to get out factors of 2 or 41, it gets out the small composites in bunches which I have to split with gp, but it does give a primality test after pulling out the small bits.
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