%I #13 Nov 23 2024 11:11:20
%S 151,241,431,641,911,3881,4751,4871,5441,5471,5641,5711,6791,6871,
%T 8831,9041,9431,10711,12721,13751,14071,14431,14591,15551,16631,16871,
%U 17231,17681,17791,18401,19031,19471,21401,25111,25391,25561,26921,27031
%N Primes p such that the multiplicative order of 2 modulo p is (p-1)/10.
%H Klaus Brockhaus, <a href="/A152310/b152310.txt">Table of n, a(n) for n=1..1000</a>
%t okQ[p_] := MultiplicativeOrder[2, p] == (p-1)/10;
%t Select[Prime[Range[10000]], okQ] (* _Jean-François Alcover_, Nov 23 2024 *)
%o (Magma) [ p: p in PrimesUpTo(27031) | r eq 1 and Order(R!2) eq q where q,r is Quotrem(p,10) where R is ResidueClassRing(p) ];
%o (PARI) Vec(select(p->((p!=2) && (znorder(Mod(2, p)) == (p-1)/10)), primes(10000))) \\ _Michel Marcus_, Feb 09 2015
%Y Cf. A115591, A001133, A001134, A001135, A001136.
%K nonn
%O 1,1
%A _Klaus Brockhaus_, Dec 02 2008