If U_n =(1+1/(n^2))(1+2^2/(n^2))^2 …(1+(n^2)/(n^2))^n, then lim_n → ∞ ( U_n )^(-4/(n^2)) is equal to:

If $\displaystyle \mathrm{U}_{\mathrm{n}}=\left(1+\frac{1}{\mathrm{n}^2}\right)\left(1+\frac{2^2}{\mathrm{n}^2}\right)^2 \ldots\left(1+\frac{\mathrm{n}^2}{\mathrm{n}^2}\right)^{\mathrm{n}}$, then $\displaystyle \lim _{\mathrm{n} \rightarrow \infty}\left(\mathrm{U}_{\mathrm{n}}\right)^{\frac{-4}{\mathrm{n}^2}}$ is equal to :