A128667 Primes p such that p^2 divides 13^(p-1) - 1.

2, 863, 1747591

Offset: 1

Author

Alexander Adamchuk, Mar 26 2007

Keywords

• bref
• hard
• more
• nonn

Comments

No further terms up to 3.127*10^13.

References

• Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See p. 233.

Links

• Amir Akbary and Sahar Siavashi, The Largest Known Wieferich Numbers, INTEGERS, 18(2018), A3. See Table 1 p. 5.
• C. K. Caldwell, Fermat quotient
• Richard Fischer, Fermat quotients B^(P-1) == 1 (mod P^2)

Crossrefs

Cf. A001220, A014127, A123692, A123693, A128668, A090968, A128669, A039951

Programs

Mathematica

Select[Prime[Range[5*10^7]], Mod[ 13^(# - 1) - 1, #^2] == 0 &] (* G. C. Greubel, Jan 18 2018 *)