A257660 Numbers n such that 13^phi(n) == 1 (mod n^2), where phi(n) = A000010(n).

2, 863, 1726, 3452, 371953, 743906, 1487812, 1747591, 1859765, 2975624, 3495182, 3719530, 5242773, 6990364, 7439060, 8737955, 10485546, 14878120, 15993979, 17475910, 20971092, 26213865, 29756240, 31987958, 34951820, 41942184, 47981937, 52427730, 59512480

Offset: 1

Author

Felix Fröhlich, Jul 26 2015

Keywords

• nonn

Comments

The subsequence of primes in this sequence is A128667.

Links

• Giovanni Resta, Table of n, a(n) for n = 1..140 (terms < 3*10^11)

Crossrefs

Cf. A077816, A128667, A241977, A241978, A242958, A242959, A242960, A245529, A253016.

Programs

Mathematica

Select[Range@ 1000000, Mod[13^EulerPhi[#], #^2] == 1 &] (* Michael De Vlieger, Jul 27 2015 *)

PARI

for(n=2, 1e9, if(Mod(13, n^2)^(eulerphi(n))==1, print1(n, ", ")))