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%I #13 Sep 26 2020 11:29:47
%S 457,1297,6481,14401,26497,44101,47521,47881,165601,225457,446881,
%T 560737,576721,677041,1037857,1049941,1649341,1903981,1934137,2291041,
%U 3990601,4110121,4262161,4663297,4736341,5293081,5317057,5372929,6410497,6535681,6651361,8122501
%N Odd integers k such that 3^((k-1)/2) == 1 (mod k*(k-2)).
%C Computed terms are prime. Is this a possible primality test or are there pseudo primes? Terms are of the form 12k+1.
%t Select[Range[3, 10^6, 2], PowerMod[3, (# - 1)/2, #*(# - 2)] == 1 &] (* _Amiram Eldar_, Sep 26 2020 *)
%o (PARI) is(n) = n%2 && n>=3 && Mod(3, n*(n-2))^((n-1)/2) == 1
%Y Cf. A081762, A337818.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Sep 26 2020
%E More terms from _Amiram Eldar_, Sep 26 2020
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