20090918, 08:23  #12 
Einyen
Dec 2003
Denmark
19×181 Posts 
p stands for prime, so its not even except for p=2. Think of it as:
2^{prime}1 Here is the proof that exponent has to be prime for 2^{p}1 can be prime: http://primes.utm.edu/notes/proofs/Theorem2.html 
20090918, 09:05  #13  
(loop (#_fork))
Feb 2006
Cambridge, England
2×7×461 Posts 
Quote:
http://www.mersennewiki.org/index.php/Primality_test is probably a good place to start. Implementing the easy algorithms is straightforward, but the hard ones can get really quite fiddly; fortunately a group at the University of Bordeaux produced parigp, where you can type Code:
? isprime(83^57+318) %4 = 1 ? nextprime(10^1000)10^1000 time = 2,785 ms. %5 = 453 Last fiddled with by fivemack on 20090918 at 09:08 

20090918, 11:20  #14 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
11·389 Posts 
Also, Wikipedia in general and this template in particular is a great source of info regarding primality tests, etc.
http://en.wikipedia.org/wiki/Templat...tic_algorithms 
20090918, 12:35  #15  
"Bob Silverman"
Nov 2003
North of Boston
2^{2}·1,877 Posts 
Quote:
Is doing a google search too much work? There is a LOT of information available. 

20090918, 12:40  #16 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
11·389 Posts 

20090918, 12:51  #17  
"Bob Silverman"
Nov 2003
North of Boston
1110101010100_{2} Posts 
Quote:
Mersenne number is, you still haven't gotten it right. Firstly, you state that P is an even number! then your example: "3, 7, 15, 31, 63, 127, 255 .... 2097151, 4194303, so forth" gives instances where P is odd!!! Don't you even know the difference between odd and even??? One has to be a total moron to state that a Mersenne number is 2^P1, where P is EVEN, then to immediately give a numerical example where P is ODD. And the expression "Subract 1 and it becomes odd, then an exponent of 2" is GIBBERISH. The phrase "then an exponent of 2" is NONSENSE. A Mersenne number is a number of the form 2^p1, where p is PRIME (i.e. not even, except for p=2). And, of course, it is clear that you never learned basic first year junior high school algebra. 2^(2k)  1 can NEVER be prime, except for k = 1. It is the difference of two squares. Where you got the idea that it might ever be prime, I have no idea. Give it up. You lack even the basic math background to dabble in this subject and you appear to be too lazy to do even a simple web search on "prime algorithms". Go back to grammar school. Come back here when you are ready to exhibit some scholarly discipline. 

20090918, 12:59  #18 
Jan 2009
Ireland
2·3·31 Posts 
if i make a statement,which is wrong.then give several examples of it which are right,i think you would have to be a moron to think that i gave correct examples without knowing what i was talking about.my statement could of been worded wrong quite easily,and i think his example shows quite clearly what a mersenne number is,even if the statement was worded incorrect,possibly by accident.
Last fiddled with by Dougal on 20090918 at 13:08 
20090918, 13:03  #19 
Jan 2009
Ireland
BA_{16} Posts 
also,one of the definitions of a mersenne number is that p is prime.another is that p is a positive integer.i could easily accuse you of not knowing your definitions.

20090918, 13:12  #20  
"Bob Silverman"
Nov 2003
North of Boston
2^{2}×1,877 Posts 
Quote:
shows that what is being written is just random nonsense. Quote:
(1) Sentences are capitalized. (2) The word "I" is capitalized. (3) How to spell. (4) Basic grammar: "could of been" > "could have been" (Although I will give the benefit of the doubt here. English may not be your first language; If it is your first language, then you are even dumber than I thought) (5) Proper names (i.e. Mersenne) are capitalized. Go away. Come back when you can write cogent sentences above 2nd grade level. Come back when you learn to read. Go back to school. Study very hard. When your IQ reaches 75, SELL. You will make a profit. 

20090918, 13:17  #21 
Aug 2006
5,987 Posts 

20090924, 21:29  #22  
Feb 2004
France
933_{10} Posts 
LLT for Fermat numbers
Quote:
Use s=5 as the seed, and do 2^n2 steps. Since 257=2^8+1=2^(2^3)+1, you need 6 steps : 5 > 23 > > 13 > 167 > 131 > 197 > 0 BINGO ! it's a prime ! (I knew that... :) Look at the proof from this page. Tony Last fiddled with by T.Rex on 20090924 at 21:30 

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