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.
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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 is always even for n>2 never true !!!!!!
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