# 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...