答案1
我用了这个答案在等式的元素之间画线。请注意,我将 放在下标中 - 我认为这样看起来是对的。但是,当然,您也可以通过将 移到 a 的前面,\tikzmark
使线条指向 a 。\tikzmark
\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{calc}
\newcommand{\tikzmark}[1]{\tikz[overlay,remember picture] \node (#1) {};}
\begin{document}
\begin{equation*}
a_{\tikzmark{a0}0}, a_{\tikzmark{a1}1}, \ldots, a_{\tikzmark{alm1}l-1}, a_{\tikzmark{al}l}, a_{\tikzmark{alp1}l+1}, \ldots, a_{\tikzmark{a2lm1}2l-1}, a_{\tikzmark{a2l}2l}, \ldots, a_{\tikzmark{a3lm1}3l-1}, a_{\tikzmark{a3l}3l}, \ldots, a_{\tikzmark{a4lm1}4l-1}
\begin{tikzpicture}[overlay,remember picture,out=315,in=225,distance=0.8cm]
\draw[-,blue,shorten >=3pt,shorten <=3pt] (a0.center) to (al.center);
\draw[-,blue,shorten >=3pt,shorten <=3pt] (a1.center) to (alp1.center);
\draw[-,blue,shorten >=3pt,shorten <=3pt] (alm1.center) to (a2lm1.center);
\draw[-,red,shorten >=3pt,shorten <=3pt] (a2l.center) to (a3l.center);
\draw[-,red,shorten >=3pt,shorten <=3pt] (a3lm1.center) to (a4lm1.center);
\end{tikzpicture}
\end{equation*}
\end{document}