[seqfan] Re: both p -/+ 2 is prime power
Neil Sloane
njasloane at gmail.com
Sat Oct 17 14:10:39 CEST 2015
With Robert GH.'s extension, that's a sequence that could be added to the
OEIS,
if someone would do it
Best regards
Neil
Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com
On Sat, Oct 17, 2015 at 8:01 AM, W. Edwin Clark <wclark at mail.usf.edu> wrote:
> On Sat, Oct 17, 2015 at 4:39 AM, Robert Gerbicz <robert.gerbicz at gmail.com>
> wrote:
>
> > 2015-10-17 10:12 GMT+02:00 W. Edwin Clark <wclark at mail.usf.edu>:
> >
> > > If p = 7 then p+2 = 9 is not prime.
> > >
> >
> > Wrong, he needs prime power, not prime.
> >
>
>
> Oops. I misread.
>
>
> > The next two terms: 450283905890997361,36472996377170786401
> > and it is likely that there is no more terms: if p>3 then p-2 or p+2 is
> > divisible by 3, but as that is a prime power it should be in the form of
> > 3^k. So we need: 3^k+2 is prime and 3^k+4 is prime power, or 3^k-2 is
> prime
> > and 3^k-4 is prime power.
> >
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> >
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