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A123692 Primes p such that p^2 divides 5^(p-1) - 1. 19
2, 20771, 40487, 53471161, 1645333507, 6692367337, 188748146801 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Dorais and Klyve proved that there are no further terms up to 9.7*10^14.

LINKS

Table of n, a(n) for n=1..7.

Chris K. Caldwell, The Prime Glossary, Fermat quotient.

Fran├žois 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.

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 *)

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

Cf. A001220, A014127, A123693, A128667, A128668, A090968, A128669, A096082.

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

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Last modified December 3 14:45 EST 2016. Contains 278745 sequences.