Exclude

Is there a number $\overline {a_1a_2 \cdots a_{2n-1}a_{2n}}$ ( $n \in \mathbb Z_+$ ) other than $\underbrace{9\cdots9}_{\text{n - 1 digits}}8\overbrace{0\cdots0}^{\text{n - 1 digits}}1$ such that the following equation is sastified?

$\large \overline {a_1a_2 \cdots a_{2n-1}a_{2n}} = (\overline{a_1 \cdots a_n} + \overline{a_{n+1} \cdots a_{2n}})^2$