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 A241921 #13 Jul 04 2021 07:53:17 %S A241921 2,1097,2243,2857,4357,6803,20747,24571 %N A241921 Numbers k such that (15^k - 4^k)/11 is prime. %C A241921 All terms are prime. %C A241921 a(9) > 10^5. %C A241921 a(1) is trivially prime, the remainder are probable primes. %t A241921 Select[Prime[Range[1, 100000]], PrimeQ[(15^# - 4^#)/11]&] %o A241921 (PARI) is(n)=ispseudoprime((15^n-4^n)/11) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A241921 Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032, A210506, A128347, A225955, A062581. %K A241921 nonn,hard,more %O A241921 1,1 %A A241921 _Robert Price_, May 01 2014