This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A250188 #13 May 21 2018 03:22:39
%S A250188 10,23,86,240,254,284,340,369,371,378,382,407,422,448,459,574,582,613,
%T A250188 619,667,686,703,767,769,844,851,875,881,944,987,995,1207,1219,1233,
%U A250188 1279,1292,1343,1372,1399,1409,1445,1468,1497,1500,1557,1586,1598,1633,1645,1677,1760,1807,1835
%N A250188 Numbers n such that Phi(39,n) is prime, where Phi is the cyclotomic polynomial.
%H A250188 G. C. Greubel, <a href="/A250188/b250188.txt">Table of n, a(n) for n = 1..10000</a>
%t A250188 Select[Range[1900], PrimeQ[Cyclotomic[39, #]] &] (* _Vincenzo Librandi_, Jan 16 2015 *)
%o A250188 (PARI) {is(n)=isprime(polcyclo(39,n))};
%o A250188 for(n=1,1000, if(is(n), print1(n, ", "))) \\ _G. C. Greubel_, May 20 2018
%Y A250188 Cf. A246392.
%K A250188 nonn
%O A250188 1,1
%A A250188 _R. J. Mathar_, Jan 12 2015