OFFSET
1,1
COMMENTS
Dorais and Klyve proved that there are no further terms up to 9.7*10^14.
a(6) and a(7) were found by Keller and Richstein (cf. Keller, Richstein, 2005). - Felix Fröhlich, Jan 06 2017
Prime terms of A242959. - Felix Fröhlich, Jan 06 2017
LINKS
Amir Akbary and Sahar Siavashi, The Largest Known Wieferich Numbers, INTEGERS, 18(2018), A3. See Table 1 p. 5.
Chris K. Caldwell, The Prime Glossary, Fermat quotient.
François G. Dorais and Dominic Klyve, A Wieferich prime search up to p < 6.7*10^15, J. Integer Seq. 14 (2011), Art. 11.9.2, 1-14.
W. Keller and J. Richstein, Solutions of the congruence a^p-1 == 1 (mod p^r), Math. Comp. 74 (2005), 927-936.
A. Paszkiewicz, A new prime p for which the least primitive root (mod p) and the least primitive root (mod p^2) are not equal, Math. Comp. 78 (2009), 1193-1195.
MATHEMATICA
Select[Prime[Range[2500]], Divisible[5^(# - 1) - 1, #^2] &] (* Alonso del Arte, Aug 01 2014 *)
Select[Prime[Range[55*10^6]], PowerMod[5, #-1, #^2]==1&] (* The program generates the first 4 terms of the sequence. *) (* Harvey P. Dale, Jan 29 2023 *)
PROG
(PARI)
N=10^9; default(primelimit, N);
forprime(n=2, N, if(Mod(5, n^2)^(n-1)==1, print1(n, ", ")));
\\ Joerg Arndt, May 01 2013
CROSSREFS
KEYWORD
hard,nonn,more
AUTHOR
Max Alekseyev, Oct 07 2006
EXTENSIONS
More terms from Alexander Adamchuk, Nov 27 2006
Updated by Max Alekseyev, Jan 29 2012
STATUS
approved