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Primes p that satisfy q^(p-1) == 1 (mod p^2), i.e., are base-q Wieferich primes, for a prime q dividing p-1.
1

%I #7 Jul 07 2022 02:09:45

%S 1093,3511,20771,1006003,1747591,5395561,53471161

%N Primes p that satisfy q^(p-1) == 1 (mod p^2), i.e., are base-q Wieferich primes, for a prime q dividing p-1.

%e p = 1747591 satisfies 13^(p-1) == 1 (mod p^2) and 13 is a factor of 1747590, so 1747591 is a term of the sequence.

%o (PARI) is(n) = my(f=factor(n-1)[, 1]~); for(k=1, #f, if(Mod(f[k], n^2)^(n-1)==1, return(1))); 0

%o forprime(p=1, , if(is(p), print1(p, ", ")))

%Y Cf. A355546.

%K nonn,hard,more

%O 1,1

%A _Felix Fröhlich_, Jul 06 2022