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 A234346 #10 Dec 24 2013 01:45:42
%S A234346 5,11,17,29,53,83,89,107,251,269,809,971,2213,2267,4373,6563,6569,
%T A234346 6803,8747,13121,19709,19763,20411,59051,65609,177173,183707,531521,
%U A234346 538001,590489,1062881,1594331,1594403,1595051,1596509,4782971,4782977,4783697,14348909
%N A234346 Primes of the form 3^k + 3^m - 1, where k and m are positive integers.
%C A234346 Clearly, all terms are congruent to 5 modulo 6.
%C A234346 By a conjecture in A234337 or A234347, this sequence should have infinitely many terms.
%C A234346 Conjecture: For any integer a > 1, there are infinitely many primes of the form a^k + a^m - 1, where k and m are positive integers.
%H A234346 Zhi-Wei Sun, <a href="/A234346/b234346.txt">Table of n, a(n) for n = 1..1000</a>
%e A234346 a(1) = 5 since 3^1 + 3^1 - 1 = 5 is prime.
%e A234346 a(2) = 11 since 3^2 + 3^1 - 1 = 11 is prime.
%t A234346 n=0;Do[If[PrimeQ[3^k+3^m-1],n=n+1;Print[n," ",3^k+3^m-1]],{m,1,310},{k,1,m}]
%Y A234346 Cf. A000040, A000079, A000244, A234309, A234310, A234337, A234344, A234347
%K A234346 nonn
%O A234346 1,1
%A A234346 _Zhi-Wei Sun_, Dec 23 2013