A277049 Primes p such that the multiplicative order of 5 modulo p is prime.

3, 11, 31, 59, 71, 149, 179, 191, 269, 359, 389, 409, 479, 569, 719, 839, 1019, 1039, 1091, 1319, 1439, 1609, 1619, 1699, 1759, 1861, 1949, 2039, 2099, 2239, 2309, 2459, 2579, 2621, 2749, 2819, 2879, 2909, 2939, 2999, 3119, 3229, 3449, 3461, 3581, 3709

Offset: 1

Author

Vincenzo Librandi, Oct 28 2016

Keywords

• nonn

Comments

Odd primes that divide 5^p-1 for some prime p. - Robert Israel, Nov 13 2016

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A277048.

Programs

Magma

[p: p in PrimesInInterval(2, 4000) | IsPrime(Modorder(5, p))];

Maple

select(p -> isprime(p) and isprime(numtheory:-order(5,p)), [3,seq(p,p=7..10000,2)]); # Robert Israel, Nov 13 2016

Mathematica

Select[Prime@Range@600, PrimeQ@MultiplicativeOrder[5, #] &]

PARI

is(n) = n!=5 && ispseudoprime(n) && ispseudoprime(znorder(Mod(5, n))) \\ Felix Fröhlich, Nov 01 2016