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 A137653 #20 Jul 28 2024 10:58:15
%S A137653 1,2,4,5,6,20,21,22,28,58,120,144,1100,1926,2892,4773,5214,17241,
%T A137653 18980,31265
%N A137653 Numbers k such that 12^k + 7 is prime.
%t A137653 Do[If[PrimeQ[(12^n+7)],Print[n]],{n,2000}]
%o A137653 (PARI) is(n)=ispseudoprime(12^n+7) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y A137653 Cf. A137652, A137654.
%K A137653 nonn,more
%O A137653 1,2
%A A137653 _Zak Seidov_, Feb 01 2008
%E A137653 a(15)-a(17) from _Jinyuan Wang_, Mar 03 2020
%E A137653 a(18)-a(19) from _Michael S. Branicky_, Mar 15 2023
%E A137653 a(20) from _Michael S. Branicky_, Jul 28 2024