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 A339923 #20 Apr 08 2021 07:19:20
%S A339923 1,2,9,24,42,74,221,620,14064,36697,152048,384558
%N A339923 Numbers k such that 14^k + 3 is prime.
%e A339923 1 is a term since 14^1 + 3 = 17 is a prime.
%t A339923 Do[ If[ PrimeQ[ 14^n + 3], Print[n]], {n, 0, 200000}]
%o A339923 (PARI) is(n)=isprime(14^n + 3)
%Y A339923 Cf. A339924.
%K A339923 nonn,more
%O A339923 1,2
%A A339923 _Paul Bourdelais_, Dec 23 2020
%E A339923 a(12) corresponds to a probable prime discovered by _Paul Bourdelais_, Jan 06 2021