Write a python function by using recursion to solve Mobius question.

(3+4+5 points) We say that a positive integer n is square-free if n is not divisible by p for any prime number p. (E.g. 15 and 37 are square-free, but 24 and 49 are not.) Con- sider the function u (named after A.F. Mbius, popularly known for his strip) defined on positive integers n as follows: u(n) if n=1 0 if n is not square-free (-1) if n is square-free and has exactly t prime divisors