[tex]\displaystyle
\frac{13}{n^3 -3^n} \\ \\
n=0 ~~\Longrightarrow~~\frac{13}{0^3 -3^0} =\frac{13}{ -1} = \boxed{-13 \in Z} \\ \\
n=2 ~~\Longrightarrow~~\frac{13}{2^3 -3^2} =\frac{13}{ 8-9} = =\frac{13}{ -1}= \boxed{-13 \in Z} \\ \\ }
\Longrightarrow ~~ \boxed{n_1 = 0~~si~~n_2=2}
[/tex]