# Paretheses should match same height on single line in multiple arrays

Given is following formula:

$a^{(k)}=\left(\begin{array}{c} a_1^{(k)}\\ \vdots\\ a_n^{(k)} \end{array}\right)\to\left(\begin{array}{c} a_1\\ \vdots\\ a_n \end{array}\right)=a$

The first vector is a little bit more height than the second one. Is it possible to have the same height for all four parentheses?

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$a^{(k)}=\left(\begin{array}{c} a_1^{(k)}\\ \vdots\\ a_n^{(k)} \end{array}\right)\to\left(\begin{array}{c} a_1^{\vphantom{(k)}}\\ \vdots\\ a_n^{\vphantom{(k)}} \end{array}\right)=a$