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Old 2015-10-15, 03:00   #2
P90 years forever!
Prime95's Avatar
Aug 2002
Yeehaw, FL

2·3,659 Posts

Originally Posted by CuriousKit View Post
I have to ask... beyond a simple curiosity, is there any reason behind attempting to factorise a Mersenne number that has already been proven to be composite? I noticed that the user "westicles" successfully found a factor in 2973,421 - 1 today (October 14th, 2015), even though it's been triple-checked with the Lucas-Lehmer primality test. Of course, the factor found in this case is 88 bits long, so is definitely an impressive find, but is there a good reason for looking for the factors in such composites?
For the fun of it. Some people like to move Mersenne numbers from the double-checked to has-a-known-factor state. Others like the even tougher challenge of moving Mersenne numbers from the has-a-known-factor state to all-factors-known state.
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