\documentclass[11pt]{scrartcl}

% vim: tw=50

\usepackage{notesheader}

{
\renewtheorem{customlemma}{Lemma}[section]
\renewtheorem{customtheorem}[customlemma]{Theorem}
\renewtheorem{customproposition}[customlemma]{Proposition}
\renewtheorem{customcorollary}[customlemma]{Corollary}
}

\begin{document}

\newcommand\coursecode{Anal}
\title{Analysis I}
\author{}
\date{\today}
\maketitle

\tableofcontents

\newpage

\inputlectures

\end{document}