$\left ( 4n - 5 \right ) \vdots \left ( n - 1 \right ) \Leftrightarrow \left ( 4n - 4 - 1 \right ) \vdots \left ( n - 1 \right ) \Leftrightarrow 4.\left ( n - 1 \right ) - 1 \vdots \left ( n - 1 \right ) \Leftrightarrow \left ( n - 1 \right ) \in Ư\left ( -1 \right ) \Leftrightarrow \left ( n - 1 \right ) \in \left \{ -1; 1 \right \} \Leftrightarrow n \in \left \{ 0; 2 \right \}$