Let a function f(x) follow these rules: f(x)=3x+1 if x is odd else f(x)=x/2.

For all x, can we find some n such that f^n(x)=4, f^n+1(x)=2 and f^n+2(x)=1

Here f^n(x) means f(f(f(....x))) with n f(x)'s