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 A339922 #19 Apr 08 2021 07:19:25
%S A339922 1,2,5,7,9,11,15,37,59,119,154,439,745,799,1260,1444,3306,8890,14604,
%T A339922 15869,20195,99055,186554,396120
%N A339922 Numbers k such that 20^k - 3 is prime.
%e A339922 1 is a term since 20^1 - 3 = 17 is a prime.
%t A339922 Do[ If[ PrimeQ[ 20^n - 3], Print[n]], {n, 0, 200000}]
%o A339922 (PARI) is(n)=isprime(20^n - 3)
%Y A339922 Cf. A339921.
%K A339922 nonn,more
%O A339922 1,2
%A A339922 _Paul Bourdelais_, Dec 23 2020
%E A339922 a(24) from _Paul Bourdelais_, Jan 28 2021