Look at the following recursive function:

f(0,0) = 1 f(0,b) = 2*f(0,b-1) f(a,0) = f(0,f(a-1,0)) f(a,b) = f(a,0)

Or if you like it with just variables and the conditions:

f(a,b) = 1 if a=0 AND b=0 f(a,b) = 2*f(a,b-1) if a=0 AND b>0 f(a,b) = f(0,f(a-1,b)) if a > 0 AND b=0 f(a,b) = f(a,0) if a>0 and b>0

What is the value of f(4,0)?

NOTE: This is not an easy recursion. If you can get this, then you certainly have recursion mastered well beyond what is needed for THIS course. But give it a shot if you want. And don't even try to determine what f(5,0) is