mersenneforum.org How to check if a number is a Mersenne prime ?
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 2004-06-18, 07:34 #1 Unregistered   24·73 Posts How to check if a number is a Mersenne prime ? What do I do if I think I have found a greater mersenne but my calculator has no way to check it, or I don't. (It can only do 2^400 or something...) Is there a fairly easy way to check whether I have one or not with a program? I tried downloading 'ntprime' but I don't know how it works, it didn't seem to do anything...
 2004-06-18, 09:20 #2 MrHappy     Dec 2003 Paisley Park & Neverland 5·37 Posts A Mersenne number (-> just check if the exponent is prime) or a Mersenne prime? For the latter: download Prime95 Version 23.8 from http://www.mersenne.org/freesoft.htm and enter the exponent in [Prime95]->[Advanced]->[Test]. If you don't see immedite progress just lower the entry in [Prime95]->[Options]->[Preferences]->[Iterations between screen outputs]. Prime95 works for exponents up to 79 300 000. MrHappy.
2004-06-18, 13:37   #3
Uncwilly
6809 > 6502

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

19×499 Posts

You can find a list of all known Mersenne primes here: http://www.utm.edu/research/primes/m...dex.html#known

Also, know that:
Quote:
 All exponents below 8,715,700 have been tested and double-checked.
This means that there are no unknown Meresenne primes lurking below that value.

 2004-06-18, 16:14 #4 Unregistered   2×3×13×79 Posts that's what u think!!
 2004-06-18, 20:40 #5 PrimeCruncher     Sep 2003 Borg HQ, Delta Quadrant 70210 Posts I think our tests are fairly conclusive. We keep testing the exponent until we get two matching residues. Version 23 implements error codes so we can tell if a test is probably bad.
 2004-06-18, 20:55 #6 Uncwilly 6809 > 6502     """"""""""""""""""" Aug 2003 101×103 Posts 948110 Posts Yes, I think that the matching residues is key here. To have these 2 large numbers to happen to match and one be an erroneous test is highly unlikely. To have 2 that have errors that match is so unlikely that it is considered to be all but magical. The actual chances are around. Having a second type of hardware with a second program check this with the same residue is considered proof for the math community.
 2004-06-19, 08:18 #7 Unregistered   6,121 Posts Ok I had the wrong program before, that one worked, thanks. I was attemptimng one much higher than 8 mil, more like 54 million or something but it wasn't even a prime number so no luck... Thanks anyway.

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