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%I #13 Sep 08 2022 08:46:10
%S 2,10,13,24,28,43,47,49,54,65,83,98,106,143,152,177,184,190,194,195,
%T 241,249,259,264,292,315,319,345,353,355,386,394,481,500,517,525,534,
%U 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 Numbers n such that Phi(38,n) is prime, where Phi is the cyclotomic polynomial.
%H G. C. Greubel, <a href="/A250187/b250187.txt">Table of n, a(n) for n = 1..10000</a>
%t Select[Range[2000], PrimeQ[(#^19 + 1) / (# + 1)] &] (* _Vincenzo Librandi_, Jan 15 2015 *)
%o (Magma) [n: n in [1..2000]| IsPrime((n^19+1) div (n+1))]; // _Vincenzo Librandi_, Jan 15 2015
%o (PARI) select(x->isprime(x), vector(1000, n, polcyclo(38, n)), 1) \\ _Michel Marcus_, Jan 15 2015
%Y Cf. A246392.
%K nonn
%O 1,1
%A _R. J. Mathar_, Jan 12 2015
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