Math & Science ⇒ Condition beneath two successive Sums

[drmath]

Hi,

I want to write "i<j" under two successive sums as centered.

Code: Select all

\begin{equation}
  \sum_{i=1}^{n-1}\sum_{j=2}^n a_{ij}
\end{equation}

Thank you for your interest in advance.

[localghost]

The amsmath package provides the \underset command.

Code: Select all

\documentclass{article}
\usepackage{mathtools}  % loads »amsmath«

\begin{document}
  \begin{equation}
    \underset{i<j}{\sum_{i=1}^{n-1}\sum_{j=2}^n} a_{ij}
  \end{equation}
\end{document}

Next time please prepare a self-contained and minimal example in order to give an adequate problem description.


Best regards and welcome to the board
Thorsten