[seqfan] Re: A relation between A153971 and A098828?
maximilian.hasler at gmail.com
Wed Jan 7 17:59:34 CET 2009
I agree that the sequence
A153971 Numbers p susch that 2^(p-1)+3 is not prime.
merits "uned", "obsc".
I observed that all listed numbers are = 11 (mod 12)
which is not the case for all primes s.th.2^(p-1)+3 is prime.
But this is not sufficient.to explain the missing terms (then starting with 47).
(Adding "primes =11 (mod 12)" one would get
Also, the comment is strange.
The "conjecture" does not merit that name (since already 37 is a
Inspired by the second part of the comment, I think I found the inteded meaning:
for(n=1,99, isprime( p = 2*n^2 + 6*n + 3 ) & !isprime(2^(p-1)+3) &
So it should be
A153971 Primes of the form p = 2*n^2 + 6*n + 3 such that 2^(p-1)+3 is
But personnally I find this a quite arbitrary definition....
On Wed, Jan 7, 2009 at 10:43 AM, Edwin Clark <eclark at math.usf.edu> wrote:
> The sequence A153971 is incorrectly defined:
> Note that if p = 6 then 2^(p-1)+3 = 35, but 6 is not in the
> listed numbers. Next guess: definition should be only primes p such that
> 2^(p-1)+3 is not prime, but then 37 should be in the list, yet it is not.
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