[Tex/LaTex] How to get \mathbb{1} to work (characteristic function of a set)

formattingmath-mode

I am trying to get the digit one printed the \mathbb{} font in math mode, however the command

\mathbb{1}

outputs some rubbish. I certainly saw the character I am after in some pdf's generated from latex, hence my question: how do you get it to work?

Best Answer

Since \mathbb doesn't support digits (with amssymb or txfonts) you may use bbm

\documentclass{article}
\usepackage{bbm}
\begin{document}
\[ \mathbbm{1} \]
\end{document}

bbm example

or dsfont, the doublestroke package:

\documentclass{article}
\usepackage{dsfont}
\begin{document}
\[ \mathds{1} \]
\end{document}

dsfont example

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