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 A250181 #16 Sep 08 2022 08:46:10 %S A250181 2,3,21,22,23,35,39,74,80,84,89,108,114,121,126,134,152,153,171,180, %T A250181 195,204,230,256,263,297,321,326,336,342,345,351,368,390,393,397,398, %U A250181 399,413,427,439,490,525,563,566,574,591,602,609,630,641,652,657,660,667,682,685,694,708,712,716,721 %N A250181 Numbers n such that Phi_26(n) is prime, where Phi is the cyclotomic polynomial. %H A250181 Robert Israel, <a href="/A250181/b250181.txt">Table of n, a(n) for n = 1..10000</a> %p A250181 select(t -> isprime((t^13+1)/(t+1)), [$1..2000]); # _Robert Israel_, Jan 15 2015 %t A250181 Select[Range[2000], PrimeQ[(#^13 + 1) / (# + 1)] &] (* _Vincenzo Librandi_, Jan 15 2015 *) %o A250181 (Magma) [n: n in [1..2000]| IsPrime((n^13+1) div (n+1))]; // _Vincenzo Librandi_, Jan 15 2015 %o A250181 (PARI) is(n)=isprime(polcyclo(26,n)) \\ _Charles R Greathouse IV_, Sep 08 2015 %Y A250181 Cf. A246397. %K A250181 nonn %O A250181 1,1 %A A250181 _R. J. Mathar_, Jan 09 2015