>Try simple cases. What do you get plugging in m = n =
>0? What do you get if only one of them is 0?
Of course it'easy to prove that f(0)=0 and f(n²)=(f(n))², even it'rather easy to calculate f(1),f(2), then f(4),f(8) , then f(5) (plug m=2,n=1), then f(3) (plug m=3,n=4) ,etc...
In fact i have calculate f(m) for m=0 to 20 and i stop to 20 because I wanted a general proof of the "obvious" fact that f(m) = m by induction, but it does'nt seem to be quite so easy
Thanks a lot if you could help me
sincerely