# Enumerate with multiple numbers (comma-separated) for a single item

I'd like to get a list that looks like this:

1. Text addressing #1.

2,3. Text addressing #2 and #3 together.



The motivation is that the list items are referring to a previous list. Any idea on how to do this easily with enumerate? (Or some other way to do it that looks consistent with the enumerate environment, i.e. if I had an enumerate list right above it, the two would seem to be formatted identically except the 2,3 part..)

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I found this interesting, and I was searching for a solution for three numbers actually. Piggybacking on egreg's answer, I came up with \newcommand{\tripleitem}{% \begingroup \stepcounter{enumi}% \edef\tmp{\theenumi, }% \stepcounter{enumi} \edef\tmpt{\theenumi, } \stepcounter{enumi} \edef\tmp{\endgroup\noexpand\item[\tmp\tmpt\labelenumi]}% \tmp} for three numbers. Perhaps someone who knows more about the language would know how to generalize it for an arbitrary number of grouped items? – Kevin Mantel Sep 3 '15 at 7:14

If you don't need greater generality, this might work:

\documentclass{article}
\newcommand{\doubleitem}{%
\begingroup
\stepcounter{enumi}%
\edef\tmp{\theenumi, }%
\stepcounter{enumi}
\edef\tmp{\endgroup\noexpand\item[\tmp\labelenumi]}%
\tmp}

\begin{document}
\begin{enumerate}
\item A
\item B
\item C
\item D
\end{enumerate}
Another
\begin{enumerate}