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A331424
Prime numbers p such that p^2 divides 31^(p-1) - 1.
2
7, 79, 6451, 2806861
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[3*10^6], PrimeQ[#] && PowerMod[31, # - 1, #^2] == 1 &] (* Amiram Eldar, May 05 2021 *)
PROG
(PARI) forprime(p=2, 1e8, if(Mod(31, p^2)^(p-1)==1, print1(p", ")))
CROSSREFS
Wieferich primes to base b: A001220 (b=2), A014127 (b=3), A123692 (b=5), A123693 (b=7), A128667 (b=13), A128668 (b=17), A090968 (b=19), A128669 (b=23), this sequence (b=31), A331426 (b=37), A331427 (b=41).
Cf. A039951.
Sequence in context: A113034 A267798 A201704 * A052385 A093947 A222137
KEYWORD
nonn,more
AUTHOR
Seiichi Manyama, Jan 16 2020
STATUS
approved