\[ \newcommand{\d}{\mathrm{d}} \newcommand{\e}{\mathrm{e}} \newcommand{\i}{\mathrm{i}} \]

A multi-index is said to be increasing if its entries are ordered in increasing order, i.e. for \(I=(i_1,\ldots,i_k)\) we have

\begin{equation*} i_1<\ldots