\documentclass[a4paper,10pt]{article}
\usepackage{myXsim}

\author{Benjamin Bertrand}
\title{Somme suites - exercises}
\date{février 2021}

\DeclareExerciseCollection{banque}
\xsimsetup{
    step=4,
}

\pagestyle{empty}

\begin{document}

\setcounter{exercise}{4}
\input{exercises.tex}
\printcollection{banque}

\end{document}