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Old 2020-11-17, 08:05   #6
Batalov
 
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"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

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Quote:
Originally Posted by YaoPlaysMC View Post
I'm using NewPGen.

The n value is 4,001,337 and the range of k I'm using is 1,000,000 to 21,000,000.

When should I stop sieving?
It depends on what you are planning to find.
▪ Plan A. You want to sieve and then you want to test all of them and find all primes (~4 or even 7-8 if you keep even k values in the sieve), then see answer above.
▪ Plan B. You want to find one prime and then stop. Then you should stop earlier (~4-8 times earlier); you should have sieved in a range which is 2-3-4 times smaller, too. Use well known estimates for density of primes and a couple pencil lines on a napkin.
▪ Plan C. Take previously sieved RPS files (they are deeper than you can ever dream to sieve), and take n>=4,001,337. Then when you do find a prime, you can always reformat it in a way that n is exactly 4,001,337 and k will be even, but so what. Your n is arbitrary anyway.

In either case, the earlier you run pencil estimates of how many core years you will need to spend , the better, maybe even before starting sieving. Do you have access to the required number of core-years?
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