base step: n=0 : ( 2 pow 0 . 2 pow 0) - 1 = 0 is divisible by 3. so the stmt is true for n=0.
inductive step: let us assume that the statement is true for any value of n. Now we have to prove that the stmt is true for n = n+1.
(2 pow n+1 . 2 pow n+1 ) - 1
2 pow (2n+2) - 1
how to solve after this step. I am struck here....