topnush
I have this MWE:
```
\documentclass{beamer}
\usepackage[many]{tcolorbox}
\usepackage{listings}
\lstdefinestyle{duckstyle}{%
moredelim=[is][\color{red}]{|}{|},
mathescape=true,
escapechar=@,
basicstyle=\ttfamily,
columns=fullflexible
}
\lstset{style=duckstyle}
\newcommand{\ubar}[1]{\alt<+>{\underaccent{\bar}{#1}}{#1}}
\tcbuselibrary{skins}
\tcbset{
% arc=0pt,
% outer arc=0pt,
colback=white,
}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,
shapes,
tikzmark, shapes.geometric}
\newcommand{\Proc}[1]{\textsc{#1}}
\newcommand{\Blue}[1]{\textcolor{varcolor}{#1}}
\definecolor{varcolor}{RGB}{15,122,183}
\begin{document}
\begin{frame}[fragile]
\begin{tcolorbox}[colback=blue!5!white, text width=4.5cm, left=7pt, right=10pt]
\begin{lstlisting}[basicstyle=\linespread{0.9}\ttfamily, mathescape,tabsize=4]
@\Proc{Foo}@(@\Blue{j}@)
\end{lstlisting}
\end{tcolorbox}
\end{frame}
\end{document}
```
I would like to replace @\Proc{Foo}@(@\Blue{j}@) with @\Proc{Foo}@(@\Blue{a_i}@) and have a_i rendered as math. How can I do that?