OFFSET
1,1
COMMENTS
To allow primes less than the specified primitive root m (here, 8) to be included, we use the essentially equivalent definition "Primes p such that the multiplicative order of m mod p is p-1". This comment applies to all of A019334-A019421. - N. J. A. Sloane, Dec 03 2019
Members of A001122 that are not congruent to 1 mod 3. - Robert Israel, Aug 12 2014
Terms are congruent to 5 or 11 modulo 24. - Jianing Song, May 12 2024
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
Let a(p,q)=sum(n=1,2*p*q,2*cos(2^n*Pi/((2*q+1)*(2*p+1)))). Then 2*p+1 is a prime of this sequence when a(p,3)==1. - Gerry Martens, May 15 2015
On Artin's conjecture, a(n) ~ (5/3A) n log n, where A = A005596 is Artin's constant. - Charles R Greathouse IV, May 21 2015
MAPLE
select(t -> isprime(t) and numtheory:-order(8, t) = t-1, [2*i+1 $ i=1..1000]); # Robert Israel, Aug 12 2014
MATHEMATICA
pr=8; Select[Prime[Range[200]], MultiplicativeOrder[pr, # ] == #-1 &] (* N. J. A. Sloane, Jun 01 2010 *)
a[p_, q_]:=Sum[2 Cos[2^n Pi/((2 q+1)(2 p+1))], {n, 1, 2 q p}]
2 Select[Range[800], Rationalize[N[a[#, 3], 20]]==1 &]+1
(* Gerry Martens, Apr 28 2015 *)
Join[{3, 5}, Select[Prime[Range[250]], PrimitiveRoot[#, 8]==8&]] (* Harvey P. Dale, Aug 10 2019 *)
PROG
(PARI) is(n)=isprime(n) && n>2 && znorder(Mod(8, n))==n-1 \\ Charles R Greathouse IV, May 21 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved