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How to look up a symbol?

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

$\mathbbm{1}$ \\

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

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marked as duplicate by egreg, Mico, percusse, Martin Schröder, Marco Daniel Aug 17 '12 at 8:01

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Does this help?: douglas.stebila.ca/blog/archives/2004/06/27/… – Jellby Jul 5 '12 at 10:59
If you load the package bbold, you can type \mathbb{1} (in math-mode, of course) to get what you want. The "standard" blackboard bold glyphs are available only for uppercase letters -- hence the need to load an extra package. – Mico Jul 5 '12 at 10:59
@Mico I believe you have answered the question. I recommend you post your comment as an answer. – azetina Jul 5 '12 at 14:34
@azetina: done! – Mico Jul 5 '12 at 15:25
up vote 6 down vote accepted

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 mathds package) will generate:

enter image description here


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