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 A158795 #16 Sep 08 2022 08:45:43
%S A158795 13,97,4801,33613,1356446145697,383162462761132828801,
%T A158795 6439811511626359453675213,5303461691719306943558046763201,
%U A158795 1498096661930372466988988205389128987297,81072431194288773664131732218033347601750444502024167492384908896001
%N A158795 Primes of the form 2*7^k - 1.
%C A158795 Values of k are in A002959.
%C A158795 All terms are of the form 12*k + 1. - _Altug Alkan_, Sep 22 2018
%H A158795 Vincenzo Librandi, <a href="/A158795/b158795.txt">Table of n, a(n) for n = 1..12</a>
%e A158795 2*7^1 - 1 = 13, 2*7^2 - 1 = 97, and 2*7^4 - 1 = 4801 are primes, but 2*7^3 - 1 = 685 is not.
%t A158795 Select[Table[2*7^n-1,{n,0,300}],PrimeQ] (* _Vincenzo Librandi_, Jul 26 2012 *)
%o A158795 (Magma) [a: n in [0..100] | IsPrime(a) where a is 2*7^n-1 ]; // _Vincenzo Librandi_, Jul 26 2012
%o A158795 (PARI) for(k=1, 1e3, if(ispseudoprime(p=2*7^k-1), print1(p, ", "))); \\ _Altug Alkan_, Sep 22 2018
%Y A158795 Cf. A002959.
%K A158795 nonn
%O A158795 1,1
%A A158795 _Vincenzo Librandi_, Mar 27 2009
%E A158795 a(7) corrected and examples edited by _Jon E. Schoenfield_, Jun 19 2010