

A123692


Primes p such that p^2 divides 5^(p1)  1.


20




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

Table of n, a(n) for n=1..7.
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, 114.
W. Keller and J. Richstein, Solutions of the congruence a^p1 == 1 (mod p^r), Math. Comp. 74 (2005), 927936.
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), 11931195.


MATHEMATICA

Select[Prime[Range[2500]], Divisible[5^(#  1)  1, #^2] &] (* Alonso del Arte, Aug 01 2014 *)


PROG

(PARI)
N=10^9; default(primelimit, N);
forprime(n=2, N, if(Mod(5, n^2)^(n1)==1, print1(n, ", ")));
\\ Joerg Arndt, May 01 2013


CROSSREFS

Cf. A001220, A014127, A123693, A128667, A128668, A090968, A128669, A096082, A242959.
Sequence in context: A173156 A214598 A242959 * A261362 A132942 A237521
Adjacent sequences: A123689 A123690 A123691 * A123693 A123694 A123695


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



