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%I #4 Mar 30 2012 17:34:28
%S 3,7,31,127,173,3313,8191,131071,524287,699053,13271393,2147483647
%N Primes in A152057.
%t Flatten[Sort[Table[If[PrimeQ[Sum[FactorInteger[2^n - 1][[m]][[1]], {m, 1, Length[FactorInteger[2^n - 1]]}]], Sum[FactorInteger[2^n - 1][[m]][[1]], {m, 1, Length[FactorInteger[2^n - 1]]}], {}], {n, 0, 50}]]]
%Y A046800
%K nonn
%O 0,1
%A _Roger L. Bagula_, Nov 22 2008
%E Edited by _N. J. A. Sloane_, Nov 26 2008