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 A217095 #27 Feb 17 2017 12:26:57 %S A217095 7,67,73,1091,1483,10937 %N A217095 Numbers n such that (10^n + 9^n)/19 is prime. %C A217095 The numbers n themselves (7, 67, 73, ...) are also prime. %C A217095 a(7) > 10^5. %t A217095 Select[ Prime[ Range[1, 100000] ], PrimeQ[ (10^# + 9^#)/19 ]& ] %o A217095 (PARI) is(n)=isprime((10^n+9^n)/19) \\ _Charles R Greathouse IV_, Feb 17 2017 %Y A217095 Cf. A057175, A125956, A128339, A181141, A187819. %K A217095 hard,nonn,more %O A217095 1,1 %A A217095 _Robert Price_, Feb 17 2013