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 A138917 #2 Mar 31 2012 12:38:15
%S A138917 79,205339,2849723505777919,
%T A138917 32630698480032300363207829406924223200028691707999878933118763629424475875983590509549306981,
%U A138917 127580191747195202924309312459314208655999588495944426207896494224749946405733526219402133007132444053184501199
%N A138917 Primes of the form (7^n - 3^n)/4.
%t A138917 a={};Do[p=(7^n-3^n)/4;If[PrimeQ[p],AppendTo[a,p]],{n,0,13^2}];a
%Y A138917 Cf. A128024.
%K A138917 nonn
%O A138917 1,1
%A A138917 _Vladimir Joseph Stephan Orlovsky_, May 16 2008