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 2018-12-05, 10:18 #1 enzocreti   Mar 2018 17×31 Posts A yuge number (2^7891456-1)*10^2375565+2^7891455-1 Is this number a probable prime or which is the smallest factor?
2018-12-05, 11:22   #2
axn

Jun 2003

3×11×149 Posts

Quote:
 Originally Posted by enzocreti Is this number a probable prime
Almost certainly not.
Quote:
 Originally Posted by enzocreti or which is the smallest factor?
Could be too big for us to find out.

Why don't you do a PRP test using PFGW and find out if it is (probable) prime or composite?

 2018-12-05, 13:23 #3 axn     Jun 2003 10011001101012 Posts No factors till 32*10^9. Quitting my attempt.
2018-12-05, 13:36   #4
science_man_88

"Forget I exist"
Jul 2009
Dumbassville

26·131 Posts

Quote:
 Originally Posted by enzocreti (2^7891456-1)*10^2375565+2^7891455-1 Is this number a probable prime or which is the smallest factor?
it won't have any factors in common with M3, M5,M11,M13, M283 , or M15413 to start. if it did then then the consecutive Mersenne numbers in question would have to share a factor. it also won't share factors with 2^15413+1 and a few other numbers. just using simple math.

2018-12-06, 11:16   #5
enzocreti

Mar 2018

17·31 Posts
Program

Quote:
 Originally Posted by axn No factors till 32*10^9. Quitting my attempt.
Can you tell me what program did you use?

2018-12-06, 13:29   #6
axn

Jun 2003

3·11·149 Posts

Quote:
 Originally Posted by enzocreti Can you tell me what program did you use?
A quick 2-line throwaway script written in PARI/GP

2018-12-06, 13:59   #7
enzocreti

Mar 2018

20F16 Posts
code

Quote:
 Originally Posted by axn A quick 2-line throwaway script written in PARI/GP

Can you give me the code?

2018-12-06, 14:42   #8
Uncwilly
6809 > 6502

"""""""""""""""""""
Aug 2003
101×103 Posts

2·5·13·73 Posts

Quote:
 Originally Posted by enzocreti Can you give me the code?
Go write it for yourself. Prove to us that you are willing to do some actual work in proving your number schemes. We have been spoonfeeding your.

Last fiddled with by Uncwilly on 2018-12-06 at 14:43

 2018-12-06, 15:45 #9 axn     Jun 2003 3×11×149 Posts Code: mod_check(p)=my(r=Mod(2,p)^7891455); (r*2-1)*Mod(10,p)^2375565+r==1 forprime(p=2,,if(mod_check(p),print(p))) Here you go...
2018-12-06, 15:50   #10
enzocreti

Mar 2018

10000011112 Posts
code

Quote:
 Originally Posted by axn Code: mod_check(p)=my(r=Mod(2,p)^7891455); (r*2-1)*Mod(10,p)^2375565+r==1 forprime(p=2,,if(mod_check(p),print(p))) Here you go...

ok thanks

 2018-12-06, 15:56 #11 Batalov     "Serge" Mar 2008 Phi(4,2^7658614+1)/2 100100101011112 Posts Why not use Sage for that, though?

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