# Proving on Euler's totient?

• August 20th 2012, 08:38 PM
musngiburger
Proving on Euler's totient?
The Euler's totient φ is known to be multiplicative. Let f be de_ned by f(n) = φ (φ (n)). Is the
• August 20th 2012, 09:44 PM
Deveno
Re: Proving on Euler's totient?
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).
• September 4th 2012, 12:02 AM
wauwau
Re: Proving on Euler's totient?
@musngiburger

since $\varphi(n)$ is always even for n>2 $gcd(\varphi(a),\varphi(b)) = 1$ never true !!!!!!