[seqfan] Re: Fwd: Primes in an exponential sequence

franktaw at netscape.net franktaw at netscape.net
Mon Feb 8 07:12:29 CET 2010

Considering that the questions of which n's have 2^n + 1 prime, and 
which have 2^n - 1 prime, are both open questions after extensive study 
(see Fermat primes and Mersenne primes), it is unlikely that anyone 
will be able to establish definitely which numbers of this form are 
prime.  The most you can expect is a result of the form "searching up 
to <N>, the only values were <list>".

Franklin T. Adams-Watters

-----Original Message-----
From: Olivier Gerard <olivier.gerard at gmail.com>

Perhaps someone has an idea on how to investigate this
for Vincenzo ?

---------- Forwarded message ----------
From: vincenzo.librandi at tin.it <vincenzo.librandi at tin.it>
Date: Sun, Feb 7, 2010 at 20:31

I only ask if the sequence
is prime if and only if
n=3 and n=118 ?


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