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 A058221 #15 Apr 23 2023 19:41:58 %S A058221 2,5,15,17,17,83,173,357,629,179,2543,8067,5619,29027,38783,99267 %N A058221 Next-to-smallest k such that 2^(2^n) - k is prime. %o A058221 (PARI) a(n) = my(N = 2^(2^n)); N - precprime(precprime(N)-1) \\ _Michel Marcus_, Jun 29 2013 %Y A058221 Cf. A058220. %K A058221 nonn,hard,more %O A058221 1,1 %A A058221 _Warren D. Smith_, Nov 30 2000 %E A058221 a(15) from _Jinyuan Wang_, Jun 06 2020 %E A058221 a(16) from _Michael S. Branicky_, Apr 23 2023