ALEA::I1/F
Arguments: last n [generic-function]
Generates a value according to the 1/f distribution with a first value <last>,
and where <n> is a parameter which defines the output scale values, i.e. :
the values will be comprised between 0 and (2^n -1).
Ex: If n=2 the values will be comprised between 0 and 3,
Ex: If n=2 the values will be comprised between 0 and 3,
If n=4 the values will be comprised between 0 and 15,
If n=7 the values will be comprised between 0 and 127.
