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 A277049 Primes p such that the multiplicative order of 5 modulo p is prime. 1

%I

%S 3,11,31,59,71,149,179,191,269,359,389,409,479,569,719,839,1019,1039,

%T 1091,1319,1439,1609,1619,1699,1759,1861,1949,2039,2099,2239,2309,

%U 2459,2579,2621,2749,2819,2879,2909,2939,2999,3119,3229,3449,3461,3581,3709

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

%C Odd primes that divide 5^p-1 for some prime p. - _Robert Israel_, Nov 13 2016

%H Robert Israel, <a href="/A277049/b277049.txt">Table of n, a(n) for n = 1..10000</a>

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

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

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

%o (PARI) is(n) = n!=5 && ispseudoprime(n) && ispseudoprime(znorder(Mod(5, n))) \\ _Felix FrÃ¶hlich_, Nov 01 2016

%Y Cf. A000040, A277048.

%K nonn

%O 1,1

%A _Vincenzo Librandi_, Oct 28 2016

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Last modified October 22 13:35 EDT 2019. Contains 328318 sequences. (Running on oeis4.)