The Euler's totient φ is known to be multiplicative. Let f be de_ned by f(n) = φ (φ (n)). Is the function f multiplicative? Prove your answer.
Follow Math Help Forum on Facebook and Google+
f will be multiplicative if gcd(a,b) = 1 implies gcd(φ(a),φ(b)) = 1. can you think of a counter-example? look at f(15).
@musngiburger since $\displaystyle \varphi(n)$ is always even for n>2 $\displaystyle gcd(\varphi(a),\varphi(b)) = 1$ never true !!!!!!
View Tag Cloud