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 A030239 #24 Apr 19 2019 05:12:46
%S A030239 1,1,1,1,1,18,12,21,102,202,826,708,502,1522,6223,3493,1063,50655,
%T A030239 10051,328426
%N A030239 a(n) is the smallest number k such that k*2^(2^n) + 1 is prime.
%C A030239 The primality test for Proth numbers can be used. - _Thomas Ordowski_, Apr 13 2019
%F A030239 a(n) = min{a : a > 0 and (a*2^2^n)! == -1 (mod a*2^2^n+1)}.
%o A030239 (PARI) isok(k, n) = isprime(k*2^(2^n) + 1);
%o A030239 a(n) = my(k=1); while (!isok(k, n), k++); k; \\ _Michel Marcus_, Apr 15 2019
%Y A030239 Cf. A080075, A080076.
%K A030239 nonn,more
%O A030239 0,6
%A A030239 Alar Leibak (aleibak(AT)cyber.ee)
%E A030239 a(11)-a(17) from _Donovan Johnson_, Mar 26 2010
%E A030239 a(18)-a(19) from _Donovan Johnson_, Jan 14 2012
%E A030239 Name edited by _Thomas Ordowski_, Apr 13 2019