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Old 2008-05-28, 11:22   #6
R. Gerbicz
 
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"Robert Gerbicz"
Oct 2005
Hungary

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Quote:
Originally Posted by ATH View Post
So perfectnumber+1 are prime for p=2,3,13 and 19 and unknown for p=132049 (79502 digits) which I trialfactored to 18*109.
Please note that if N=2^(p-1)*(2^p-1)+1 (where Mp=2^p-1 is a Mersenne prime), then the primefactorization of N-1 is known so a quick exact primetest is possible.

Last fiddled with by R. Gerbicz on 2008-05-28 at 11:23
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