Definition:Nontotient

Definition
A nontotient is a positive even integer $n$ such that:
 * $\nexists m \in \Z_{>0}: \map \phi m = n$

where $\map \phi m$ denotes the Euler $\phi$ function.

That is, a nontotient is a positive even integer which is not the totient of any positive integer.

Also see

 * Euler Phi Function is Even for Argument greater than 2


 * Definition:Totient


 * Definition:Cototient
 * Definition:Noncototient