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 A250187 #13 Sep 08 2022 08:46:10 %S A250187 2,10,13,24,28,43,47,49,54,65,83,98,106,143,152,177,184,190,194,195, %T A250187 241,249,259,264,292,315,319,345,353,355,386,394,481,500,517,525,534, %U A250187 535,556,595,601,649,656,680,686,687,697,707,710,756,798,804,817,818,829,839,841,858,864,891,906,912,932,948,973,991,994,1012 %N A250187 Numbers n such that Phi(38,n) is prime, where Phi is the cyclotomic polynomial. %H A250187 G. C. Greubel, <a href="/A250187/b250187.txt">Table of n, a(n) for n = 1..10000</a> %t A250187 Select[Range[2000], PrimeQ[(#^19 + 1) / (# + 1)] &] (* _Vincenzo Librandi_, Jan 15 2015 *) %o A250187 (Magma) [n: n in [1..2000]| IsPrime((n^19+1) div (n+1))]; // _Vincenzo Librandi_, Jan 15 2015 %o A250187 (PARI) select(x->isprime(x), vector(1000, n, polcyclo(38, n)), 1) \\ _Michel Marcus_, Jan 15 2015 %Y A250187 Cf. A246392. %K A250187 nonn %O A250187 1,1 %A A250187 _R. J. Mathar_, Jan 12 2015