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 A199191 #17 May 13 2023 13:51:12 %S A199191 2,3,4,5,6,10,11,41,83,160,178,526,881,2578,3772,11873 %N A199191 Numbers k such that 3^(2k-3) + 3^(k-1) + 1 is prime. %C A199191 Numbers k such that A198410(k) is prime. %t A199191 Select[Range[250], PrimeQ[((3^(#-1) + 1)^3 -1)/3^#]&] %Y A199191 Cf. A198410, A199192. %K A199191 nonn,hard,more %O A199191 1,1 %A A199191 _Michel Lagneau_, Nov 03 2011 %E A199191 a(16) from _Michael S. Branicky_, May 12 2023