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 A159261 #2 Mar 30 2012 17:22:54
%S A159261 5,13,173,2111,665773,
%T A159261 3142394278117397493736691789093238367784438314557856426157
%N A159261 Primes of the form 1 + sum_{i=1..n} 2^prime[i] for some n.
%C A159261 Primes whose binary representation has the 0 and prime bits set up to prime(n). The values of n are in A159260.
%t A159261 s=1; Reap[Do[s=s+2^Prime[n]; If[PrimeQ[s], Sow[s]], {n,50}]][[2,1]]
%K A159261 nonn
%O A159261 1,1
%A A159261 _T. D. Noe_, Apr 07 2009