What element has a H-like spectrum, whose lines have wavelengths nine times shorter than those of atomic hydrogen ?

$$\begin{gathered} \frac{1}{\mathrm{\lambda }}={\mathrm{RZ}}^2\left[\frac{1}{{\mathrm{n}}_1^2}-\frac{1}{{\mathrm{n}}_2^2}\right] \\ \frac{1}{{\mathrm{\lambda }}_{\mathrm{H}}}=\mathrm{R}\times 1^2\left[\frac{1}{{\mathrm{n}}_1^2}-\frac{1}{{\mathrm{n}}_2^2}\right] ----\left(\mathrm{a}\right) \\ \frac{1}{{\mathrm{\lambda }}_{\mathrm{X}}}={\mathrm{RZ}}^2\left[\frac{1}{{\mathrm{n}}_1^2}-\frac{1}{{\mathrm{n}}_2^2}\right] ----\left(\mathrm{b}\right) \\ \mathrm{Dividing} \left(\mathrm{a}\right) \mathrm{by} \left(\mathrm{b}\right) \mathrm{we} \mathrm{get} \\ \frac{{\mathrm{\lambda }}_{\mathrm{x}}}{{\mathrm{\lambda }}_{\mathrm{H}}}=\frac{1}{{\mathrm{Z}}^2} \\ \frac{1}{9}=\frac{1}{{\mathrm{Z}}^2} \\ \mathrm{Z}=3 \mathrm{means} {\mathrm{Li}}^{+2} \mathrm{ion} \end{gathered}$$