Other primes thread
 

I think I'm starting a thread like in RPS here for non-riesel primes found by NPLB members/special riesel primes found by others.

--nuggetprime

First prime
 

Found 6th largest Generalized Woodall Prime:
91850*19^91850-1 is prime!

This is one of only 3 top-5000 primes found by phil's phrot and the first bigger/top5000 discovery for Geoff's phrot port for linux.

--nuggetprime

[quote=nuggetprime;145557]Found 6th largest Generalized Woodall Prime:
91850*19^91850-1 is prime!

This is one of only 3 top-5000 primes found by phil's phrot and the first bigger/top5000 discovery for Geoff's phrot port for linux.

--nuggetprime[/quote]


Great idea nugget! VERY nice find! It's nice to see primes discovered in other bases.

Nearly breaking Kosmaj's GW record:
146478*19^146478-1 is prime!:banana:(187315 digits)

Now 2nd largest GW.

--nuggetprime

The new world record
 

As you may have already noticed, a few days ago I found the largest known GW prime:
189620*19^189620-1 is prime!:anurag:(242483 digits)

--nuggetprime

[quote=nuggetprime;148242]As you may have already noticed, a few days ago I found the largest known GW prime:
189620*19^189620-1 is prime!:anurag:(242483 digits)

--nuggetprime[/quote]


Tremendous nugget! Way to go! Top of the heap now. :smile:

[URL="http://primes.utm.edu/primes/page.php?id=85789"]5*2^2460482-1[/URL]

[quote=em99010pepe;149860][URL="http://primes.utm.edu/primes/page.php?id=85789"]5*2^2460482-1[/URL][/quote]


So THAT is where Benson has been at all this time!

I guess for a score of 423, it was worth it. That equals about 100 of our n=550K primes! :surprised

It will move him up to #17 on the scores list at top-5000. If you remove the people who have found < 5 primes, he'd be #3!

Benson, can you help push our 1st drive a little? lol


Gary

Something smells extremely fishy about this recent huge submission:

[URL]http://primes.utm.edu/primes/page.php?id=86270[/URL]

First time searcher...huge prime...at or near power-of-10 k and n-value...I've seen this kind of thing before and I'm thinking not! It looks like a "wannabe" prime. But who knows? Stranger things have happened!

I'm putting a slow sore on sieving it to at least P=10G to see if I can save the top-5000 site a little time. I know they do trial factoring before primality testing but I don't know if they sieve. I ran srsieve to P=300M with no factors found and now have it on sr1sieve, which appears will take ~5-10 mins. to build a Legendre symbol table before starting a much faster sieve.

If it turns out to be prime, I'll be the first to retract my first para. here.


Gary

[quote=gd_barnes;159466]Something smells extremely fishy about this recent huge submission:

[URL]http://primes.utm.edu/primes/page.php?id=86270[/URL]

First time searcher...huge prime...at or near power-of-10 k and n-value...I've seen this kind of thing before and I'm thinking not! It looks like a "wannabe" prime. But who knows? Stranger things have happened!

I'm putting a slow sore on sieving it to at least P=10G to see if I can save the top-5000 site a little time. I know they do trial factoring before primality testing but I don't know if they sieve. I ran srsieve to P=300M with no factors found and now have it on sr1sieve, which appears will take ~5-10 mins. to build a Legendre symbol table before starting a much faster sieve.

If it turns out to be prime, I'll be the first to retract my first para. here.


Gary[/quote]


I ended up sieving 100000005*2^10000000-1 to P=25G...no factors found.

I just now saw that the submission was proven composite...no surprise there. See [URL]http://primes.utm.edu/primes/page.php?id=86270[/URL]. Also, another "smaller" submission for 1767766^32768+1 by the same person at [URL]http://primes.utm.edu/primes/page.php?id=86278[/URL] was also proven composite.

It's clear that he did some sieving and then submitted them without primality testing hoping that they were prime. In doing that, he wasted over a day worth of CPU time at the top-5000 site causing the proof of all of our legitimate submissions to slow down greatly. (I observed this.)

Mr. Musatov, you are a bane to the prime-searching community! Put in the CPU time like everyone else! :mad:


Gary

[quote=gd_barnes;159678]I ended up sieving 100000005*2^10000000-1 to P=25G...no factors found.

I just now saw that the submission was proven composite...no surprise there. See [URL]http://primes.utm.edu/primes/page.php?id=86270[/URL]. Also, another "smaller" submission for 1767766^32768+1 by the same person at [URL]http://primes.utm.edu/primes/page.php?id=86278[/URL] was also proven composite.

It's clear that he did some sieving and then submitted them without primality testing hoping that they were prime. In doing that, he wasted over a day worth of CPU time at the top-5000 site causing the proof of all of our legitimate submissions to slow down greatly. (I observed this.)

Mr. Musatov, you are a bane to the prime-searching community! Put in the CPU time like everyone else! :mad:


Gary[/quote]
I think users will get banned at the top-5000 site if they submit too many composite primes. Not sure exactly how many's the limit though.

[quote=mdettweiler;159717]I think users will get banned at the top-5000 site if they submit too many composite primes. Not sure exactly how many's the limit though.[/quote]
There's probably not a hard limit, it's probably more about whether they're obviously submitting things known not to be prime, like this one, whereas someone like us with many primes might get away with a couple of typos or CPU errors producing primes.

I was submitting a prime when the 3MM digit prime was being verified. I emailed Dr Caldwell because my prime was taking over 7 hours to verify. Dr Caldwell was none to happy about the 3MM digit prime because it was tying up the verification process on other submissions. He told me he had to put another machine on doing verifications because this prime had everything stymied. So, he knows about it.

Who got an email from Dr Caldwell about Musatov false primes? He is asking for help to deal with this type of situation.

[quote=em99010pepe;160247]Who got an email from Dr Caldwell about Musatov false primes? He is asking for help to deal with this type of situation.[/quote]


I got that Email. I was also the one who notified him early this morning to delete Mustov, all of his accounts, and all of his obviously composite entries. He did just that.

I'm sure he'd like if I posted his Email here since he is asking for help, so here is a cut-and-paste of it:

[quote]
Folks, I have a real problem. Martin M. Musatov is swamping my
primes.utm.edu site with false prime. His vandalism has really made
mess of the list. He first had confused a benchmark timer in proth.exe
with a primality test. Now he writes

From: Chris Caldwell
Subject: False primes
Sent: Jan 24, 2009 12:59 AM
> Why are you still submitting false primes?

From: Martin M. Musatov
[EMAIL="m.mm@vzw.blackberry.net"]m.mm@vzw.blackberry.net[/EMAIL]
Sorry, that was not intentional. I am trying to figure some things
out. Was 334928^262144+1 composite? Proth says no small factors.
Sent from my Verizon Wireless BlackBerry


I deleted his account and poof codes, he recreated them. I have blocked
the last IP addresses he was using, but he found a forth while I was
sleeping. I will delete all again in a few moments, and hack a line in
my code to block sending a password to his address, but I suspect he'll
get another soon. (And I have a meeting coming up, so it may b hours
rather than minutes.)

I could moderate all submissions to the list, but there would be long
slow periods as I was busy or traveling... folks like the quick
turn-a-round.

So I am asking here for any ideas. I know it is the wrong list, but
this group is often clever and even headed....

Chris
[/quote]

I suggested that he factor or sieve a little more before going into primality testing but that would not have helped the 2 submissions that took a long time recently.

To try to help out and allow an early deletion of the 1st large entry with no small factors, I sieved it to P=25G; no factors found. I then sieved the GFN that was taking all of last night to primality test to P=20*10^15 (20 quadrillion) over night on a very slow machine. Unfortunately, also no small factors. I stopped it after he went ahead and deleted the entry anyway.

I don't know what else to suggest to him than what he has already come up with above.

If anyone else has any ideas, I'm sure he would appreciate it.


Gary

Maybe automatically block any account with the name Musatov. (If there happens to be another Musatov that's a legitimate prime finder, he can contact you.)
Maybe some sort of smarter priority for which submissions are checked first could at least minimize the impact on verifying real primes.
Perhaps if somebody has more than one prime to verify or submits a large prime (over position 1000? I don't really know what would be a very reasonable amount), it would require Dr Caldwell's approval to verify. Or instead of simply 'more than one' or 'over position x', something that estimates the verification time for all submitted primes as 'over time x', i.e. if it'll take a while to verify all prime(s) make Caldwell have to okay it first; since this won't happen as often as every single prime, it wouldn't be unreasonable to force an extra wait for those before it shows up on the list. This would have to consider primes submitted separate times in addition to multiple primes at once.

[quote=em99010pepe;160247]Who got an email from Dr Caldwell about Musatov false primes? He is asking for help to deal with this type of situation.[/quote]
everyone on the primeform mailing list

for some reason i cant submit my new prime
is this something to do with the composites problem?
only two have been submited today and they were really early today
edit: wierd tried again and the username and password box appeared this time

Maybe each prime submitted over a certain size has to be 'countersigned' by someone already on the list. The person already on the list gets an email, when they reply with their password or something the prime-checking starts. Sounds a bit clumsy though.

Didn't know where to post this so I'll put it here. Maybe we need a Mathematics for Dummies thread.

Question #1 for MFD: If twins are in the form of k*2^n-1 and k*2^n+1, then why don't we test all our prime found to see if it is a twin? Please remember geniuses, this is Mathematics for Dummies and I epitomize the title.

[quote=MyDogBuster;168443]Didn't know where to post this so I'll put it here. Maybe we need a Mathematics for Dummies thread.

Question #1 for MFD: If twins are in the form of k*2^n-1 and k*2^n+1, then why don't we test all our prime found to see if it is a twin? Please remember geniuses, this is Mathematics for Dummies and I epitomize the title.[/quote]

I had the same thought almost immediately after getting into prime searching. Therefore at that time, I checked Riesel primes for k<1200 for twins up to n=260K. (k=1200 is as far as the Proth list goes.)

It actually required no testing. I just cut-and-pasted lists of Riesel and Proth primes up to that limit into a spreadsheet and matched them up. Proth primes can be found at [URL="http://www.prothsearch.net"]www.prothsearch.net[/URL]. The largest twin that I found in doing this comparison was 915*2^11455+1 and -1. It had already been found, much to my chagrin. I found many more larger twins for higher k's. See below.

The chances of a prime found having a twin for n>260K are EXTREMELY remote. The largest twin at this point in history is at n=195K. It has a 10-digit k.

In order for k*2^n+1 and k*2^n-1 to be prime the k-value must be divisible by 3. So if you're up for comparing the Riesel and Proth lists, limit your comparison to k's divisible by 3 and n>260K.

With the few # of primes for n>260K and only 200 k's to check (600 odd k's divided by 3), you'll quickly see that far more k's are needed to have a reasonable shot at a twin.

Now...if you want to expand your search beyond the Prothsearch list, you could use the top-5000 site and test all Riesel's for any k-value that is divisible by 3.

I think Karsten has probably done something along these lines too. You might also check with him.

One more thing: I think you might find a couple of my web pages interesting:

Twins for k<100K and n<48K:
[URL]http://gbarnes017.googlepages.com/twins100K.htm[/URL]

Twins for k<1M and n=10K-48K:
[URL]http://gbarnes017.googlepages.com/twins1M.htm[/URL]

I have sieved files up to n=60K for these efforts. n=48K-52K is in midstream of testing on one of my quads. I stopped it about 7-8 months ago to focus on NPLB and CRUS.


Gary

Thanks Gary.

So basically, if I find a prime with a k divisible by 3, I could test for a twin but probably won't find one. Can't hurt though. I may even find one.

[quote=MyDogBuster;168453]Thanks Gary.

So basically, if I find a prime with a k divisible by 3, I could test for a twin but probably won't find one. Can't hurt though. I may even find one.[/quote]

You betcha!

My suggestion would be to take a group of Riesel primes where k's are divisible by 3 and sieve them using srsieve for the Proth form up to some low limit. Usually the sieve will eliminate either all of them or all but a few of them.

To avoid redundant checking, for anything k<1200, stick to n>260K because I've already checked up to n=260K. For higher k's, which our 8th/9th/10th drives have plenty of primes for now, you could start at n=48K. That is as high as I've gotten in my testing of all k<1M.

Come to think of it, an excellent starting point would be the n=50K-200K portion of our 9th drive. 80% of the k's are > 1200 and all n are > 48K. That would be by far the most effective place to start because we already have the primes sorted nicely by k-value. After that, continuing with the n=200K-350K portion of that drive would be good because all k's are > 1200. There you go! :smile:

Any twin for n>~80K makes the top-20 list at top-5000 and is reportable! I have one for n=100K with a 10-digit k.


Gary

Just a side note. On my independent work, I just submitted 9615*2^991347-1. A nice juicy one. 298430 digits.

My largest prime ever.

Way to go! A nice one! We've been missing the really big ones lately.

[QUOTE=MyDogBuster;177777]Just a side note. On my independent work, I just submitted 9615*2^991347-1. A nice juicy one. 298430 digits.

My largest prime ever.[/QUOTE]

A nice one indeed Ian! :smile:

One thing I forgot to mention: That one was PrimeSearch/NPLB's largest prime also! :smile:

[QUOTE]One thing I forgot to mention: That one was PrimeSearch/NPLB's largest prime also! :smile:[/QUOTE]

Does that mean I get a bonus on my next check? LOL

[QUOTE=MyDogBuster;177991]Does that mean I get a bonus on my next check? LOL[/QUOTE]

... the next 'check' of a candidate? :grin: YESSSSSSSS!

[quote=gd_barnes;168454] Come to think of it, an excellent starting point would be the n=50K-200K portion of our 9th drive. 80% of the k's are > 1200 and all n are > 48K. That would be by far the most effective place to start because we already have the primes sorted nicely by k-value. After that, continuing with the n=200K-350K portion of that drive would be good because all k's are > 1200. There you go! :smile:[/quote]
Is there any good way to take the list of primes and sieve their +1 sides? I put it all in a spreadsheet to to eliminate the excess info (who found it, etc.), eliminate non-0 mod 3 candidates, and change it to +1. This gives a file with lines like "1005*2^149604+1". I just put it into PFGW with the -f option (to factor 'em first). (at about k=1500, or half of the way, already!) Is there a better way to easily get such a list into a proper sieving program? (I probably won't have time to use it instead for this check of drive 9, but if we're going to do more, as discussed [URL="http://www.mersenneforum.org/showthread.php?p=193367#post193367"]over in this thread[/URL], it'd be nice to know)
I'll post or edit this when I finish so everyone can know that the drive 9 primes have been checked for twins...
Edit: :sad: I just realized I eliminated n != 0 mod 3, instead of k != 0 mod 3. Restarting...Edit 2: Included the n=200K-350K primes from drive 9, too.

[quote=Mini-Geek;193456]Is there any good way to take the list of primes and sieve their +1 sides? I put it all in a spreadsheet to to eliminate the excess info (who found it, etc.), eliminate non-0 mod 3 candidates, and change it to +1. This gives a file with lines like "1005*2^149604+1". I just put it into PFGW with the -f option (to factor 'em first). (at about k=1500, or half of the way, already!) Is there a better way to easily get such a list into a proper sieving program? (I probably won't have time to use it instead for this check of drive 9, but if we're going to do more, as discussed [URL="http://www.mersenneforum.org/showthread.php?p=193367#post193367"]over in this thread[/URL], it'd be nice to know)[/quote]
I was able to get it into an ABCD format (or NewPGen or anything else), so sr2sieve can sieve it starting at 1995 (the largest k) but couldn't find a good way to get it sieved up to there...
Any suggestions? SRsieve (I've got 0.6.9) is crashing when printing lines like this: "removed candidate sequence 1137*2^n+1 from the sieve", so that isn't working right to get the sieve started.
Edit: Never mind, updated my srsieve and it finished to 1e6 without a problem. :smile:

Done, no primes.

Interesting. I had already done most of what you did 2 years ago for the top 5000 primes at that time. It took me quite a while and involved a lot of manual work. I encountered some of the same problems that you did so I had to resort to running multiple instances of srsieve or doing tests individually. It's nice to know that sr(x)sieve can handle multiple different forms where a k gets completely eliminated due to small factors now with the more recent releases. I seem to remember that the problem happened when there was just 1-2 primes of a specific k and the sieve eliminated all of them. It happened sometimes but not all of the time.

If you're really bold, you could try testing for twins on the entire top-5000 database including the as of now, primes that are no longer top 5000. Due to the manual effort involved, I only did about 60-70% of the top 5000 at that time and none of the non-top-5000 at the time. You could even tweak your script or whatever to test for Sophie-Germains (SGs) or their Sierp equivalent; I can't remember what the latter are called. That would be cool if you found something. SGs have the exact same chance of occurring as twins but are not nearly as popular for searching so it takes a much lower one to make the top 20.

One thing to keep in mind on twins that helped me out that perhaps you already thought of: The k must be divisible by 3. Before sieving, I put the primes in a spreadsheet, parsed out the k-value, put a column in for the k-value mod 3, and eliminated all k's where the 2nd column was not a 0. That helped me eliminate a fair percentage of them without even testing. Something similar may apply to SGs.

Edit: I also took lists of primes from Karsten's pages. That's another source that you could use. I remember finding an n=~10K twin for k=915, although it wasn't big enough to make the top 20 twins at the time, which required an exponent of n=~66K. There are likely many primes on his lists that never made top 5000, especially for some of the huge k's that the RPS folks tested way-back-when, that would be big enough to make the top 20 if they turned out to be twin or SG.


Gary