如何在 LaTeX 中写出格雷厄姆数？

Question

我想用 LaTeX 写出这张图片，但每次尝试都以失败告终。如能得到帮助，我将不胜感激。

Answer 1

好问题。:-)

\documentclass{article}
\usepackage{mathtools}

\makeatletter
\newcommand{\cdotfill}{%
  \leavevmode
  \cleaders\hb@[email protected]{\hss\textperiodcentered\hss}\hfill
  \kern\z@
}
\makeatother

\newcommand{\uparrows}[1]{% #1 is a length
  \mathrel{\underbrace{\makebox[#1][s]{$\uparrow\uparrow$\cdotfill$\uparrow$}}}%
}

\begin{document}

\[
\left.
\setlength{\arraycolsep}{0pt}
\renewcommand{\arraystretch}{1.2}
\begin{array}{rc}
G={}
& 3 \uparrows{7em} 3 \\
& 3 \uparrows{6em} 3 \\
& \underbrace{\makebox[5em]{\vdots}} \\
& 3 \uparrows{4em} 3\\
& 3 \uparrow\uparrow\uparrow\uparrow 3
\end{array}
\right\}
64\text{ layers}
\]

\end{document}

稍微调整一下长度：

\documentclass{article}
\usepackage{mathtools}

\makeatletter
\newcommand{\cdotfill}{%
  \leavevmode
  \cleaders\hb@[email protected]{\hss\textperiodcentered\hss}\hfill
  \kern\z@
}
\makeatother

\newcommand{\uparrows}[1]{% #1 is a length
  \mathrel{\underbrace{\makebox[#1][s]{$\uparrow\uparrow$\cdotfill$\uparrow$}}}%
}

\begin{document}

\[
\left.
\setlength{\arraycolsep}{0pt}
\renewcommand{\arraystretch}{1.2}
\begin{array}{rc}
G={}
& 3 \uparrows{9em} 3 \\
& 3 \uparrows{7.5em} 3 \\
& \underbrace{\makebox[6em]{\vdots}} \\
& 3 \uparrows{4.5em} 3\\
& 3 \uparrow\uparrow\uparrow\uparrow 3
\end{array}
\right\}
64\text{ layers}
\]

\end{document}