Smallest prime factor of (2^prime(n) + 1) / 3.

Terms

a(0) =3a(1) =11a(2) =43a(3) =683a(4) =2731a(5) =43691a(6) =174763a(7) =2796203a(8) =59a(9) =715827883a(10) =1777a(11) =83a(13) =283a(14) =107a(15) =2833a(17) =7327657a(18) =56409643a(19) =1753a(21) =499a(22) =179a(23) =971a(25) =415141630193a(26) =643a(27) =104124649a(28) =227