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 A216889 #21 Aug 27 2022 03:16:53 %S A216889 0,1,2,5,13,14,38,200,248,884,1004,1253,1634,3305,3521,9601,19784, %T A216889 72697 %N A216889 Numbers k such that 12*3^k + 1 is prime. %C A216889 a(19) > 2*10^5. - _Robert Price_, Mar 16 2014 %C A216889 All terms are verified primes (i.e., not merely probable primes). - _Robert Price_, Mar 16 2014 %F A216889 a(n) = A005537(n+1) - 1. - _Bruno Berselli_, Sep 27 2012 %t A216889 Select[Range[4000], PrimeQ[12 * 3^# + 1] &] %o A216889 (Magma) [n: n in [0..4000] | IsPrime(12*3^n + 1)]; %o A216889 (PARI) is(n)=ispseudoprime(12*3^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A216889 Cf. A003306, A005537-A005539, A056805. %K A216889 nonn,more %O A216889 1,3 %A A216889 _Vincenzo Librandi_, Sep 26 2012 %E A216889 a(16)-a(17) from _Vincenzo Librandi_, Sep 30 2012 %E A216889 a(18) from _Robert Price_, Mar 16 2014