\documentclass[a5paper 10pt]{article}
\usepackage{myXsim}

\usepackage{fp}
\usepackage{ifthen}

\setlength\parindent{0pt}

\author{Benjamin Bertrand}
\title{Logarithme - Cours}
\date{avril 2021}

\newcounter{mycount}

\newcommand\tablelog{%
\setcounter{mycount}{0}

\begin{multicols}{6}
    \whiledo{\value{mycount}<310}
    {
        \stepcounter{mycount}%
        \stepcounter{mycount}%
        \makebox[4em]{\themycount}% steps the counter and typesets the value of t
        \FPln{\natlogoft}{\themycount}
        \FPeval{\res}{round(\natlogoft, 3)}\res\\
    }% calculates Ln(t) and typsets it
\end{multicols}
}

\begin{document}

% the counter for the loop
% the command that stores logarithms

\begin{center}
    \textbf{Table du log en base $e$}
\end{center}
\tablelog


\vfill

\begin{center}
    \textbf{Table du log en base $e$}
\end{center}
\tablelog


% the counter for the loop

\end{document}