How to skip an \item in sub-enumerate level

Question

I would like to skip an \item in a sub-enumerate level. More specifically, I want the output to look something like:

1. 
     a)
     b)
     e)
     f)
     etc.

2.

However, when I use \addtocounter{enumi} (within the first \begin{enumerate} \end{enumerate} block obviously), it increases the outer counter and I get:

1. 
     a)
     b)
     c)
     d)
     etc. (no skips!)

3.

So I am looking for a way to specify which counter to increase. Greatly appreciate the help!

Answer 1

There's a counter for each level:

\documentclass{article}
\begin{document}
\begin{enumerate}
  \item \mbox{}
  \begin{enumerate}
    \item
    \item \addtocounter{enumii}{2}
    \item
    \item
  \end{enumerate}
  \item
\end{enumerate}
\end{document}

In the default document class(es), enumi controls the enumeration at level 1, enumii for level 2, enumiii for level 3 and enumiv for level 4.

Answer 2

You can refer to the current enumeration counter by \@enumctr:

\documentclass{article}

\makeatletter
\newcommand{\skipitems}[1]{%
  \addtocounter{\@enumctr}{#1}%
}
\makeatother

\begin{document}
\begin{enumerate}
  \item Outer
  \begin{enumerate}
    \item Inner
    \item Inner again
    \skipitems{2}
    \item Inner again
    \skipitems{3}
    \item Inner again
  \end{enumerate}
  \item Outer again
  \skipitems{1}
  \item Let's end here
\end{enumerate}
\end{document}