20100507, 11:58  #1 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
17×251 Posts 
no twin left behind?
I was just thinking about this again:
http://www.mersenneforum.org/showthread.php?t=12591 (looking for twin primes by searching the 'other side', i.e. swapping 1 and +1, of a known prime) But the top 5000 list has so many different prime forms, and is only accessible through text or HTML (both of which would not be terribly easy to extract the essentials from) it'd be nontrivial to get a list of candidates to test. So then I thought of NPLB: tons of primes, all in the form k*2^n1, all in a central DB that can pick out the k and n for me. Easy! I'd like to apply this idea to the full list of NPLB primes. NPLB has found 6604 (as of this writing) primes for 1, and I'd like to find if any of those have a twin on the +1 side. I could try to download all the pages and extract the k and n, but I figured it'd be easier to ask one of you with DB access to dump the list for me. (consider it requested preferably in the NewPGen format of one "k n" per line) 6604 candidates of all sizes before any sieving is sure to reduce to a handful of testable candidates. TBH I'm not too hopeful that such a twin does exist, but it'd be such an easy check it's almost a waste to look for new primes to find their twins before checking old primes to see if they have twins. Last fiddled with by MiniGeek on 20100507 at 12:26 
20100507, 13:24  #2 
Mar 2006
Germany
2754_{10} Posts 
You can also obtain an even greater list from my RieselPrimeDatabase for download here!
I've just updated this list (and the twinslist, too). It's in the npgformat sorted by nvalues for all primes in all summarypages. Last fiddled with by kar_bon on 20100507 at 13:24 
20100507, 13:55  #3 
"Forget I exist"
Jul 2009
Dumbassville
2^{6}×131 Posts 
stupid mouse failure lol (using mousekeys).
(10:46) gp > for(n=1,10,for(k=1,10,if(isprime(k*2^n1) && isprime(k*2^n+1),print(k"*"2"^"n"+ or 1")))) 2*2^1+ or 1 3*2^1+ or 1 6*2^1+ or 1 9*2^1+ or 1 1*2^2+ or 1 3*2^2+ or 1 9*2^3+ or 1 6*2^5+ or 1 3*2^6+ or 1 9*2^7+ or 1 (10:46) gp > this what you want ? 
20100507, 14:54  #4 
Mar 2006
Germany
2×3^{4}×17 Posts 
No, I think not!
Those small twins are all known (see list at download or the summarypages). He was asking of higher nlevels say n~500000 for any prime of the form k*2^n1. Test those k/npairs if the number k*2^n+1 is prime, too! The Rieselside (1) is known to be prime for many values here but none has ever tested the '+1'side! OTOH the chance for finding a new twin by testing only these primes is very low. Last fiddled with by kar_bon on 20100507 at 14:54 
20100507, 15:12  #5  
A Sunny Moo
Aug 2007
USA (GMT5)
3×2,083 Posts 
Quote:


20100507, 15:34  #6  
"Forget I exist"
Jul 2009
Dumbassville
2^{6}·131 Posts 
Quote:
the hard part is a prime check loop I think if I use Iczelion's win32 ASM tutorials. I did buy a ASM book though but it's for HLA might have to adapt it to win32, or someone else can try this as I suck at it lol. Last fiddled with by science_man_88 on 20100507 at 15:47 

20100507, 15:47  #7 
A Sunny Moo
Aug 2007
USA (GMT5)
3·2,083 Posts 
If you don't mind my asking, why bother using MouseKeys in the first place (since if it's that annoying, I'm assuming you don't need it for accessibility reasons)?

20100507, 15:50  #8 
"Forget I exist"
Jul 2009
Dumbassville
8384_{10} Posts 
I'm using mousekeys because my mouse stopped working so outside of speech it's the only way I know to have a way to click thinks.

20100507, 15:53  #9  
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
4267_{10} Posts 
Quote:
No, what Karsten said. Unless for some reason there're any primes in the DB but not in Karsten's list, no I don't need NPLB's list. Thanks anyway. 

20100507, 17:55  #10 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
17×251 Posts 
Status update: I'm currently at n=119k. I've found a decent number of twins that aren't in Karsten's list, but the largest is only 42932385 832 (42932385*2^8321 and +1 for FactorDB entries), which at 259 digits is not even close to making any notable twin prime lists. I'll send the full list of total and new twins when I'm done checking all numbers.
Last fiddled with by MiniGeek on 20100507 at 17:59 
20100507, 18:00  #11 
Mar 2006
Germany
2×3^{4}×17 Posts 

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