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 A013598 #12 Nov 28 2016 05:13:19
%S A013598 1,2,2,2,2,8,4,16,2,4,2,20,16,8,2,2,26,34,10,56,8,56,4,32,2,14,2,16,
%T A013598 26,130,4,16,70,70,34,22,2,50,8,82,118,70,4,52,8,46,68,52,56,16,28,34,
%U A013598 50,26,28,20,62,4,158,64,16,34,122,2,92,64,28,230,20
%N A013598 a(n) = nextprime(3^n)-3^n.
%H A013598 Zak Seidov, <a href="/A013598/b013598.txt">Table of n, a(n) for n = 0..1000</a>
%F A013598 a(n) = A151800(3^n)-3^n = A013632(3^n). - _R. J. Mathar_, Nov 28 2016
%p A013598 seq(nextprime(3^i)-3^i,i=0..100);
%t A013598 np[n_]:=Module[{c=3^n},NextPrime[c]-c]; Array[np,80,0] (* _Harvey P. Dale_, Jul 14 2014 *)
%Y A013598 Cf. A013604.
%K A013598 nonn
%O A013598 0,2
%A A013598 James Kilfiger (mapdn(AT)csv.warwick.ac.uk)
%E A013598 Corrected by _Harvey P. Dale_, Jul 14 2014