I wrote:
> > From: Simon Rubinstein-Salzedo [mailto:[EMAIL PROTECTED]]
>
> > Last night I was reading a number theory textbook, and I
> > thought of this odd conjecture: is one more than the
> > primorial of a Mersenne prime always a prime? I wouldn't
> > have a clue where to start on proving it, so if anyone
> > had any ideas, I'd appreciate it. Thanks.
>
> You would probably find it difficult to prove, not least
> because it's false.
>
> According to Caldwell's lists, the only primorial+1 primes,
> p#+1, for p< 100000 are
> p=2, 3, 5, 7, 11, 31, 379, 1019, 1021, 2657, 3229, 4547,
> 4787, 11549, 13649, 18523, 23801, 24029 and 42209
>
> I don't see the Mersenne prime 257 in there.
I was too hasty. 257 is the index in a Mersenne prime, not a Mersenne
prime itself.
However, M7 = 127 is prime, but 127 isn't in the list either, so I still
have a counterexample for you. Neither is M13 = 8191.
Paul
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