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 A159262 #2 Mar 30 2012 17:22:54
%S A159262 2,3,7,11,19,191,709,1597,16421
%N A159262 Largest prime appearing as an exponent in the sum in A159261.
%t A159262 s=1; Reap[Do[s=s+2^Prime[n]; If[PrimeQ[s], Sow[Prime[n]]], {n,2000}]][[2,1]]
%K A159262 nonn
%O A159262 1,1
%A A159262 _T. D. Noe_, Apr 07 2009