\documentclass[]{article}

\usepackage{amsmath}
\usepackage{tikz}
\usepackage{listings}

\usepackage{pagecolor}
\usepackage{xcolor}
\color{green}
\newcommand{\HO}[1]{%
	\begin{tikzpicture}[#1]%
		\draw  (0,1.3ex) -- (3ex,1.3ex);%
		\draw (1.5ex,1ex) -- (1.5ex,1.6ex);%
	\end{tikzpicture}%
}
\newcommand{\IHO}[1]{%
	\begin{tikzpicture}[#1]%
		\draw (0,0.2ex) -- (3ex,0.2ex);%
		\draw [line width=0.6mm] (1.5ex,0.001ex) -- (1.5ex,0.08ex);%
	\end{tikzpicture}%
}

\begin{document}
	\pagecolor{black}
	
	\section{Notation}
	
	\subsection{Hyperoperation}
	
	\begin{equation}
		a+b = a {\overset{1}{\HO{scale=2}}} b
	\end{equation}
	
	\begin{equation}
		\label{hyperoperator}
		a {\overset{n}{\HO{scale=2}}} a {\overset{n}{\HO{scale=2}}} … a = a {\overset{n+1}{\HO{scale=2}}} b
	\end{equation}
	
	\subsection{Inverse-hyperoperation}
	
	\begin{equation}
		c \overset{1}{\IHO{scale=2}} b =c-b
	\end{equation}
	
	\begin{equation}
		\label{hyperoperator}
		c {\overset{n}{\IHO{scale=2}}} b = a
	\end{equation}
	
\end{document}