Math summation symbol in LaTeX

There are two styles of displaying the summation symbol:

1. Compressed format. Compressed to fit onto one line. Such as: $\sum_{n=1}^{10} n^{2}$
2. Full format. In a larger, more readable format. Such as: $\displaystyle\sum_{n=1}^{10} n^{2}$

The way to control the display style:

• Compressed format

\sum_{n=1}^{10} n^{2} 

• Full format

\displaystyle\sum_{n=1}^{10} n^{2}

Refs:

1. http://timmurphy.org/2009/08/15/math-summation-symbol-in-latex/