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 A213216 #21 Feb 20 2017 14:46:19 %S A213216 47,401,509,8609 %N A213216 Numbers n such that (12^n + 11^n)/23 is prime. %C A213216 All terms are prime. %C A213216 a(5) > 10^5. %t A213216 Select[ Prime[ Range[1, 100000] ], PrimeQ[ (12^# + 11^#)/23 ]& ] %o A213216 (PARI) is(n)=ispseudoprime((12^n+11^n)/23) \\ _Charles R Greathouse IV_, Feb 20 2017 %Y A213216 Cf. A057178, A128341, A181141, A187819, A217095. %K A213216 hard,nonn,more %O A213216 1,1 %A A213216 _Robert Price_, Mar 02 2013 %E A213216 Removed incorrect first term of "2".