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Old 2021-03-22, 17:18   #13
Viliam Furik
 
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"Viliam Furík"
Jul 2018
Martin, Slovakia

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The pattern you observed is fairly trivial I would say. If the prime exponent you're testing modulo p is itself a Mersenne prime, then you are testing the Mersenne prime with a smaller exponent. For all Mersenne primes, S(x) (for x >= p) is equal to 2, because S(p-2) = 0 (mod p), S(p-1) = -2 (mod p), and S(p) = 2 (mod p).

So if there can be such a test for Mersenne numbers modulo p, it won't work for double Mersennes.
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