A273727 Numbers k such that 3k - 1 divides 3^k - 1 and 3 does not divide k.
1, 175952, 348880, 649078, 951625, 1495472, 1944320, 3140852, 3483200, 3643270, 4359040, 4703776, 6513584, 8170904, 9854200, 11005568, 11831890, 12149872, 12828200, 12910928, 18095630, 18964400, 22034516, 43599424, 62849024, 66322480, 82159588, 85181600
Offset: 1
Keywords
Programs
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Mathematica
Select[Range[10^6], Mod[#,3] > 0 && PowerMod[3, #, 3*#-1] == 1 &] (* Giovanni Resta, May 29 2016 *)
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PARI
is(n)=n%3 && Mod(3,3*n-1)^n==1 \\ Charles R Greathouse IV, May 29 2016