The issue gizmo and I see with the sequence is that it is all ones if the first element is 2 - 1 = 1.
Are you supposed to start with 2^2 - 1 = 3; then 2^3 - 1 = 7; 2^7 - 1 = 127; etc? Those do seem to be all prime.
Are you supposed to start with 2^2 - 1 = 3; then 2^3 - 1 = 7; 2^7 - 1 = 127; etc? Those do seem to be all prime.