Freaky Function!
Algebra
Level
3
A function \(f: \mathbb{N} \rightarrow \mathbb{N}\) is such that
1) \(f(xy)= f(x)f(y)\)
2) The function is strictly increasing.
3) \(f(2)=2\)
Find \(\sum _{ k=1 }^{ 20 }{ f(k) } \)
by
Mehul Arora