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 A186104 #38 Sep 03 2025 20:09:52 %S A186104 2,17,107,647,23327,139967,30233087,6530347007,39182082047, %T A186104 14215144014964850687,240614901699187213221099227578367, %U A186104 53193679461858262403856737876228196870083927814929645567 %N A186104 Primes of the form 3*6^k - 1. %H A186104 Charles R Greathouse IV, <a href="/A186104/b186104.txt">Table of n, a(n) for n = 1..21</a> %o A186104 (Magma) [3*6^n-1: n in [0..140] | IsPrime(3*6^n-1)]; // _Bruno Berselli_, Feb 12 2011 %o A186104 (PARI) v=[];for(n=0,1e3,if(ispseudoprime(k=3*6^n-1),v=concat(v,k)));v \\ _Charles R Greathouse IV_, Jul 26 2011 %Y A186104 For the exponents k see A186106. %K A186104 nonn,changed %O A186104 1,1 %A A186104 _Gilbert Mozzo_, Feb 12 2011 %E A186104 Edited by _N. J. A. Sloane_, Feb 12 2011