Which level of the single ionized carbon has the same energy as the ground state energy of hydrogen atom?

Energy of $H$ -atom is $E=-13.6Z^2/n^2$ for $H$-atom $Z=1$ and for ground state, $n=1$

$\Rightarrow E=-13.6\times \frac{1^2}{1^2}=-13.6 eV$

Now for carbon atom (single ionised), $Z=6$

$E=-13.6\frac{Z^2}{n^2}=-13.6$ (given)

$\Rightarrow n^2=6^2\Rightarrow n=6$