%I #12 Sep 08 2022 08:46:02
%S 5,37,73,101,109,197,257,577,601,641,677,727,1601,1801,2593,3137,3389,
%T 3457,4057,4357,5477,8101,8837,10369,14401,14407,16901,17957,18253,
%U 18433,20809,21317,22501,25601,30977,33857,37447,42437,44101,47629,47653,50177
%N Primes p such that the order of 2 mod p is a square.
%H Vincenzo Librandi, <a href="/A213049/b213049.txt">Table of n, a(n) for n = 1..178</a>
%e The order of 2 mod 601 is 25, which is a square, so 601 is a term.
%o (PARI)
%o { forprime (p=3, 10^6,
%o r = znorder(Mod(2,p));
%o if ( issquare(r), print1(p,", ") );
%o ); }
%o (Magma) [NthPrime(n): n in [2..6275] | IsSquare(Modorder(2, NthPrime(n)))]; // _Bruno Berselli_, Jun 08 2012
%Y Cf. A014662, A014663, A122094.
%K nonn
%O 1,1
%A _Joerg Arndt_, Jun 03 2012