Ellipsis with sideways curly bracket

Like this?

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
    \underbrace{A \times A \times A \times \dots \times A}_{n \text{ times}}
\end{equation}
\end{document}

I think you're looking to use the \overbrace{...}^{...} macro.

\documentclass{article}
\usepackage{amsmath}  % for '\overbrace' macro
\begin{document}
\[
\overbrace{A\times A\times\dots\times A\times A}^{\text{$n$ times}}
\]
\end{document}

For later, and if you have a lot of them, lmake package does nice patterns.

MWE

\documentclass{article}
\usepackage{amsmath}
\usepackage{lmake}
\begin{document}
\Large

\[ \lmake[A_{\i}, \!] \]

\[ \lmake[A_{\i}, \,] \]

\[ \lmake[{A_{\i}}, \times] \]

\[ \lmake[\left(\frac{\i}{\i+1}\right),\!]\]

\end{document}