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Old 2020-01-24, 15:07   #291
Dr Sardonicus
 
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Feb 2017
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Once upon a time, long long ago, I noted that if n > 2 and k < 2n+2 + 2, the fact that N = k*2n+2 + 1 divides Fn in and of itself proves N is prime. In the case at hand (n = 5523858), k = 13 satisfies this condition.

Last fiddled with by Dr Sardonicus on 2020-01-24 at 15:08 Reason: Omit unnecessary words!
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