Brack algorithm

At each step

            X2=l+Dup´Fmult

The value of Fmult starts at Fact = 1.17

On each step it increases as

            Fmult=Fmult*Fact

On the last step, Ntry, Fmult = FactNtry.

On this step, X2 should be Endc

(1.1)

Define

           (1.2)