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 A098873 #5 Apr 02 2018 16:35:14
%S A098873 1,1,2,1,1,1,1,4,1,5,1,34,7,1,1,1,2,2,1,1,1,1,4,24,8,1,10,7,1,1,2,1,3,
%T A098873 2,1,1,1,2,1,1,1,1,28,5,2,2484,1,2,1,1
%N A098873 Least k such that 2*((6*n)^k) - 1 is prime.
%e A098873 2*((6*1)^1) - 1 = 11 prime, so a(1)=1
%e A098873 2*((6*2)^1) - 1 = 23 prime, so a(2)=1
%e A098873 2*((6*3)^1) - 1 = 35 = 5*7
%e A098873 2*((6*3)^2) - 1 = 647 prime, so a(3)=2
%t A098873 lk[n_]:=Module[{k=1},While[!PrimeQ[2((6n)^k)-1],k++];k]; Array[lk,50] (* _Harvey P. Dale_, Apr 02 2018 *)
%K A098873 nonn
%O A098873 1,3
%A A098873 _Pierre CAMI_, Oct 13 2004
%E A098873 Corrected by _Harvey P. Dale_, Apr 02 2018