A250188 - OEIS

%I #13 May 21 2018 03:22:39

%S 10,23,86,240,254,284,340,369,371,378,382,407,422,448,459,574,582,613,

%T 619,667,686,703,767,769,844,851,875,881,944,987,995,1207,1219,1233,

%U 1279,1292,1343,1372,1399,1409,1445,1468,1497,1500,1557,1586,1598,1633,1645,1677,1760,1807,1835

%N Numbers n such that Phi(39,n) is prime, where Phi is the cyclotomic polynomial.

%H G. C. Greubel, <a href="/A250188/b250188.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[1900], PrimeQ[Cyclotomic[39, #]] &] (* _Vincenzo Librandi_, Jan 16 2015 *)

%o (PARI) {is(n)=isprime(polcyclo(39,n))};

%o for(n=1,1000, if(is(n), print1(n, ", "))) \\ _G. C. Greubel_, May 20 2018

%Y Cf. A246392.

%K nonn

%O 1,1

%A _R. J. Mathar_, Jan 12 2015