mersenneforum.org GIMPS and Fibonacci prime project?
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 2017-10-25, 07:42 #1 Shen   Jan 2017 316 Posts GIMPS and Fibonacci prime project? I have run prime95 for several years, as many of you, I didn't find one prime, that makes me a little disappointed. At the same time, I do some research on Fibonacci prime, it seems a little easier to find one prime or PRP. There are 15 PRP and 34 primes , 49 totally until now. Could someone set up a project for Fibonacci prime like GIMPS?
2017-10-25, 10:46   #2
science_man_88

"Forget I exist"
Jul 2009
Dumbassville

20C016 Posts

Quote:
 Originally Posted by Shen I have run prime95 for several years, as many of you, I didn't find one prime, that makes me a little disappointed. At the same time, I do some research on Fibonacci prime, it seems a little easier to find one prime or PRP. There are 15 PRP and 34 primes , 49 totally until now. Could someone set up a project for Fibonacci prime like GIMPS?
you already can find they must be in specific positions, when done mod 6 the fibonacci sequence is 0,1,1,2,3,5,2,1,3,4,1,5,0,5,5,4,3,1,4,5,3,2,5,1,0,1,1,2,... repeats. So, the indexes that could be primes greater than 3 are 1,2,5,7,10,11,13,14,17,19,22,23 mod 24.

2017-10-25, 13:50   #3
Dr Sardonicus

Feb 2017
Nowhere

29×157 Posts

Quote:
 Originally Posted by science_man_88 you already can find they must be in specific positions, when done mod 6 the fibonacci sequence is 0,1,1,2,3,5,2,1,3,4,1,5,0,5,5,4,3,1,4,5,3,2,5,1,0,1,1,2,... repeats. So, the indexes that could be primes greater than 3 are 1,2,5,7,10,11,13,14,17,19,22,23 mod 24.
Since

Fa | Fab,

Fa > 1 for a > 2,

F2k = Fk*Lk, and Lk > 1 for k > 1,

it is clear that Fn can be prime only if n = 4, or if n is prime.

I did find a page of Possible Fibonacci Primes listing some large Fibonacci PRP's, but it hasn't been updated in 11 years...

2017-10-25, 14:13   #4
paulunderwood

Sep 2002
Database er0rr

3,677 Posts

Quote:
 Originally Posted by Dr Sardonicus I did find a page of Possible Fibonacci Primes listing some large Fibonacci PRP's, but it hasn't been updated in 11 years...

 2017-10-25, 15:35 #5 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 24×3×7×19 Posts The problem is that Fibonacci numbers aren't the right shape for group-theoretic primality proofs, and nobody's seriously interested in finding large PRPs.
2017-10-25, 15:39   #6
chris2be8

Sep 2009

37738 Posts

Quote:
 Originally Posted by Dr Sardonicus I did find a page of Possible Fibonacci Primes listing some large Fibonacci PRP's, but it hasn't been updated in 11 years...
Fibonacci (104911) is prime, see http://factordb.com/index.php?query=I%28104911%29 . The other 3 PRPs listed are still PRP in factordb.

Chris

2017-10-25, 20:59   #7
Dr Sardonicus

Feb 2017
Nowhere

29×157 Posts

Quote:
 Originally Posted by fivemack The problem is that Fibonacci numbers aren't the right shape for group-theoretic primality proofs, and nobody's seriously interested in finding large PRPs.
People are, however, actively working on composite factors of Fibonacci and Lucas numbers that are, perhaps barely, within the range of present factoring methods.

See, e,g, posts 2201 and 2205 to the thread NFS@Home.

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