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Old 2019-01-06, 20:39   #7
Blackadder
 
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"Angelino Desmet"
Mar 2018
Belgium

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Quote:
Originally Posted by science_man_88 View Post
no number divisible by a number other than 1 or itself is prime. Now, 2p-2 = 2(2p-1-1) therefore is divisible by 2

there is only one exception: when p-1 = 1 (and p=2) -- 2p-1-1 = 1 doesn't hurt primality.
That makes sense. Thank you.
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