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 A186687 #9 Sep 08 2022 08:45:55
%S A186687 2,17,41,107,251,647,761,1511,23327,27431,139967,3145721,30233087,
%T A186687 35551871,6530347007,39182082047,91424858111,146766805631,
%U A186687 6847552083566591,153558654482644991,246511875008397311,14215144014964850687
%N A186687 Primes of the form k*6^m - 1, where k is a Mersenne prime (A000668) and m >= 0.
%C A186687 Twin of A185167.
%e A186687 (2^1279-1)*6^1047-1 is prime.
%t A186687 Union[Flatten[Table[Select[p*6^Range[0, 30] - 1, # < 10^20 && PrimeQ[#] &], {p, {3, 7, 31, 127, 8191, 131071, 524287, 2147483647, 2305843009213693951}}]]]
%o A186687 (Magma)
%o A186687 [n: n in [0..3000] | IsPrime((2^1279-1)*6^n-1)];
%Y A186687 Cf. A186104, A186105, A185069, A185167.
%K A186687 nonn
%O A186687 1,1
%A A186687 _Gilbert Mozzo_, Feb 25 2011