# [Tex/LaTex] Smashoperator on two limits of sums

math-modemath-operatorsvertical alignment

# Problem

This MWE with two sums, that have prolonged limits each:

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}

\begin{document}
$\displaystyle x \wedge y = \sum_{1 \leq i_1 < \ldots < i_p \leq n} \sum_{1 \leq j_1 < \ldots < j_q \leq n} a_{i_1 \ldots i_p} b_{j_1 \ldots j_q} \; \underbrace{e_{i_1} \wedge \ldots \wedge e_{i_p} \wedge e_{j_1} \wedge \ldots \wedge e_{j_q}}_{\text{is sometimes 0}}$
\end{document}


produces a lot of space for the sums. Nevertheless the readability is bad, as the limits are too close to each other. Usage of smashoperator{} will lead to an error and one limit not showing any more.
I would much prefer the second formula (or also additionally smashed on the left side of the first sum).

# Question

How can I produce the second formula in the picture? (or any other nice looking 'smashed' result)

## Edit

1) I found this (just the sums) code to be close to my desired result. However it yields an undefined control sequence error:

\smashoperator{\mathop{\smashoperator{\sum_{1 \leq i_1 < \ldots < i_p \leq n}\sum}}_{\qquad 1 \leq j_1 < \ldots < j_q \leq n}}


#### Best Answer

Maybe this? with a little help from \mathclap and stackengine. EDIT to replace \ldots with \dots and \cdots, per Mico's request. I hope I interpreted his request in the right way...

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{stackengine}
\stackMath
\begin{document}
$\displaystyle x \wedge y =\qquad \sum_{\mathclap{1 \leq i_1 < \dots < i_p \leq n}}\quad \sum_{\stackunder[5pt]{}{\scriptstyle\mathclap{1 \leq j_1 < \dots < j_q \leq n}}} a_{i_1 \dots i_p} b_{j_1 \dots j_q} \; \underbrace{e_{i_1} \wedge \cdots \wedge e_{i_p} \wedge e_{j_1} \wedge \cdots \wedge e_{j_q}}_{\text{is sometimes 0}}$
\end{document}