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-   -   Sierpinski/Riesel Base 5: Post Primes Here (https://www.mersenneforum.org/showthread.php?t=3125)

 axn 2005-06-21 11:06

136588*5^22917-1 is prime!

 axn 2005-06-22 03:43

43156*5^44135-1 is prime!

 axn 2005-06-23 03:35

294698*5^47110-1 is prime!

 jaat 2005-07-18 16:55

Another one bites the dust

Prime 9164*5^40892-1

Is there some other way to check these are primes. As the test has some chance of being wrong.(Am i right?)

8494 and 38348 completed upto 50k without any luck.

Btw, Is there some statistics/guesses as to how many will fall till say 50k?
I got 2/4.

jaat

 rogue 2005-07-18 17:54

[QUOTE=jaat]Another one bites the dust

Prime 9164*5^40892-1

Is there some other way to check these are primes. As the test has some chance of being wrong.(Am i right?)[/QUOTE]

Yes, you can use WinPFGW to do a primality test with the -tp switch (or -tm for a +1 number). No, unless there is a bug in the software or if there were a hardware problem, the number is prime.

 geoff 2005-07-19 09:40

[QUOTE=jaat]Btw, Is there some statistics/guesses as to how many will fall till say 50k?
I got 2/4.[/QUOTE]
From the Sierpinski data so far I would guess that a little more than 1 in 3 candidates will be eliminated by finding a prime with an exponent between 20,000 and 50,000. The 4 candidates you worked on were of average combined weight, so I would say you did just a little better than average to eliminate 2.

(I moved the last two messages from the reservations thread)

 jaat 2005-07-19 20:21

Thanks to both Rogue and geoff for answering the queries. I checked both the numbers with the WinPFGW and they are prime. It is also nice to know that one can knock a very large fraction of them very quickly. I'll get back to them soon.

jaat

 geoff 2005-08-14 05:31

I wondered if any of the primes we find could be one of a pair of twin primes of the form k*5^n+/-1.

Since in any three consecutive integers one must be divisible by 3, for both k*5^n+1 and k*5^n-1 to be prime, k must be divisible by 3. It turns out that this is possible for just one of the k we are currently testing, the Riesel candidate k=151026.

Of the primes already found, the two largest twin primes of this form were 110538*5^139+/-1 and 136674*5^172+/-1.

 OmbooHankvald 2005-09-15 07:29

Hey all. I was wondering: Is this project still "alive"? There is not a lot going on in the forum and only geoff has found primes in the last month, so I started to wonder how many people (or GHz) are working on this problem?

I think I'll get back here when I'm finished with my 2721...

 geoff 2005-09-17 15:16

I have a part time 2.66GHz P4 that I split between this project and PSP, it usually does 8-10 hours per week.

It is quiet at the moment, but that is OK, there is no rush :-)

 axn 2005-10-11 07:47

99356*5^34994-1 is prime!

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