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 A211409 #14 Jun 13 2017 13:48:01 %S A211409 3,5,7,11,17,19,41,53,109,167,2207,3623,5059,5471,7949,21211,32993, %T A211409 60251 %N A211409 Numbers n such that (9^n + 4^n)/13 is prime. %C A211409 All terms are prime. %C A211409 The next element, a(19), is greater than 10^5. %t A211409 Select[ Prime[ Range[1, 100000] ], PrimeQ[ (9^# + 4^#)/13 ]& ] %o A211409 (PARI) is(n)=ispseudoprime((9^n+4^n)/13) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A211409 cf. A181141, A128339, A057175, A125956, A187819. %K A211409 more,nonn %O A211409 1,1 %A A211409 _Robert Price_, Feb 09 2013