1. Very nice!

2. Thank you for that small tip. Just thought about investing an hour how to write this down properly.

3. Dário

This may be usefull:

\renewcommand{\O}[1]{$\mathcal{O}(#1)$}
• tom

Thanks, interesting suggestion! Here is a minimal working example for illustration:

\documentclass[11pt]{article}
\renewcommand{\O}[1]{$\mathcal{O}(#1)$}
\begin{document}
\O{n}
\end{document}
• JouleV

It is very nice, but I would define a new command so that the original meaning of \O (which gives us Ø) is not lost. So I would do like this

\newcommand\bigO[1]{$\mathcal{O}(#1)$}
• A good point, thanks much. Best, Tom

4. Ajay Makwana

thank you