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A ring of odd primes

by steiner1745
Tags: primes, ring
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Jul2-11, 09:28 PM
P: 1
I got this question from another
forum and it's driving me crazy.
Find all triples of odd primes,
p,q,r such that
p^2+1 is divisible by q, q^2+1 is divisible by r
and r^2+1 is divisible by p.
Two such triples are 5,13,17
and 17,29,421. If we assume
p<q<r, then there are no other
such triples with p<10^7.
Are there any others?
Anyone have any ideas?
From quadratic residue theory
we know that p,q,r are all
congruent to 1(mod 4).
Can we say more?
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Jul6-11, 01:15 PM
micromass's Avatar
P: 18,346
(2,5,13) also works...
Jul6-11, 10:26 PM
P: 460
Quote Quote by micromass View Post
(2,5,13) also works...
nice observation but 2 is not an odd prime.

Years ago i thought i solved the BEAL CONJECTURE because i found 3^5 + 10^2 = 7^3

Then my math prof. pointed out ALL exponents must be integers greater than 2.

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