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