exponential function

a(2)^r = 1       2^r = 1/a 

a(128)^r = 5     a(2⁷)^r = 5

                       a (1/a)⁷ =5

                          1/a⁶ = 5

                           1/5 = a⁶

                                  a = .76472449              .764724491 * (2^r) = 1      r = .38699