A260507 Primes p such that (2^p+1)^(p-1) == 1 (mod p^2).

2, 7, 179, 619, 17807

Offset

1,1

Comments

A000040(n) such that A260531(n) = 1.

Is this a subsequence of A130060?

a(6) > 10325801 if it exists.

a(6) > 3037000499 if it exists. - Hiroaki Yamanouchi, Aug 20 2015

Links

Table of n, a(n) for n=1..5.

Example

2^7 + 1 = 129 and 129^6 == 1 (mod 7^2), so 7 is a term of the sequence.

Mathematica

Select[Prime@ Range@ 120, Mod[(2^# + 1)^(# - 1), #^2] == 1 &] (* Michael De Vlieger, Jul 29 2015 *)

Prog

(PARI) forprime(p=2, , if(Mod(2^p+1, p^2)^(p-1)==1, print1(p, ", ")))

Crossrefs

Cf. A098640, A127074, A130060, A130062, A260531.

Sequence in context: A159034 A336249 A120381 * A173240 A042359 A015174

Adjacent sequences: A260504 A260505 A260506 * A260508 A260509 A260510

Keyword

nonn,hard,more

Author

Felix Fröhlich, Jul 27 2015

Status

approved