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Old 2013-07-20, 11:34   #1
mart_r
 
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Dec 2008
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Default Given sigma(n)-n, find the smallest possible n

For example, for large enough odd sigma(n)-n, it's quite easy to find a possible n. It doesn't take long to find a prime p such that q=(sigma(n)-n-1-p) is also prime and n=p*q is found.
The problem now is determining whether this is the smallest solution (mostly it isn't), and how efficiently can it be found?
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