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%I #31 Jul 19 2024 08:41:49
%S 1,2,3,5,7,9,11,13,17,19,23,25,27,29,31,37,41,43,47,49,53,59,61,67,71,
%T 73,79,81,83,89,97,101,103,107,109,113,121,125,127,131,137,139,149,
%U 151,157,163,167,169,173,179,181,191,193,197,199,211,223,227,229
%N Union of 2 and powers of odd primes.
%C Numbers n such that the group G_n:={x+yi: x^2+y^2==1 (mod n); 0<=x,y<n} is cyclic; i.e., numbers n such that A060968(n) = A235863(n).
%H Jose María Grau, A. M. Oller-Marcen, Manuel Rodriguez and D. Sadornil, <a href="http://arxiv.org/abs/1401.4708">Fermat test with Gaussian base and Gaussian pseudoprimes</a>, arXiv:1401.4708 [math.NT], 2014.
%F {2} UNION A061345. - _R. J. Mathar_, Jul 19 2024
%t Select[ Range[230], # == 2 || Mod[#, 2] == 1 && PrimeNu[#] < 2 &] (* and modified by _Robert G. Wilson v_, Dec 29 2016 *)
%Y Cf. A060968, A061345, A235863.
%K nonn
%O 1,2
%A _José María Grau Ribas_, Feb 23 2014