%I M5221 N2271 #26 Sep 08 2022 08:44:28
%S 31,223,433,439,457,727,919,1327,1399,1423,1471,1831,1999,2017,2287,
%T 2383,2671,2767,2791,2953,3271,3343,3457,3463,3607,3631,3823,3889,
%U 4129,4423,4519,4567,4663,4729,4759,5167,5449,5503,5953,6007,6079,6151,6217,6271,6673,6961,6967,7321
%N Primes p such that the multiplicative order of 2 modulo p is (p-1)/6.
%D M. Kraitchik, Recherches sur la Théorie des Nombres. Gauthiers-Villars, Paris, Vol. 1, 1924, Vol. 2, 1929, see Vol. 1, p. 59.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H T. D. Noe, <a href="/A001136/b001136.txt">Table of n, a(n) for n = 1..1000</a>
%t Reap[For[p = 2, p < 10^4, p = NextPrime[p], If[MultiplicativeOrder[2, p] == (p - 1)/6, Sow[p]]]][[2, 1]] (* _Jean-François Alcover_, Dec 10 2015, adapted from PARI *)
%o (Magma) [ p: p in PrimesUpTo(6079) | r eq 1 and Order(R!2) eq q where q,r is Quotrem(p,6) where R is ResidueClassRing(p) ]; // _Klaus Brockhaus_, Dec 02 2008
%o (PARI) forprime(p=3,10^4,if(znorder(Mod(2,p))==(p-1)/6,print1(p,", "))); \\ _Joerg Arndt_, May 17 2013
%Y Cf. A001133.
%K nonn
%O 1,1
%A _N. J. A. Sloane_
%E More terms and better definition from _Don Reble_, Mar 11 2006