[Tex/LaTex] Unity element 1

symbols

Possible Duplicate:
How to look up a symbol?

I'd like to write the unity element 1 in LaTeX. I have tried these methods:

$\mathbbm{1}$ \\
$\mathbb{1}$\\
$\mathbbss{1}$\\
$\mathbbtt{1}$\\
$\mathds{1}$\

but I receive the integer 1. I think that I'm missing a suitable package. How to solve this problem?

Best Answer

The "standard" blackboard bold math font contains only uppercase latin-alphabet letters. To get a blackboard bold "1" symbol, you need to load an additional LaTeX package.

For instance, the commands \mathbb{1} (load the bbold package) and \mathds{1} (load the dsfont package) will generate:

enter image description here

respectively.