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Old 2020-07-25, 15:49   #5
paulunderwood
 
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Sep 2002
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Consider x^2-2*x-1=0. This has solutions x= 1 +- sqrt(2). But 2^((W-1)/2) == -1 mod W where W=(2^p+1)/3 because kronecker(2,W) == -1. I propose the test:

Mod(Mod(1,W)*x,x^2-2*x-1)^(W+1)==-1 for Wagstaffs.

Last fiddled with by paulunderwood on 2020-07-25 at 15:54
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