# Indicator function sign [duplicate]

Whenever I need the indicator function I use (for example) the following syntax

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\begin{document}
\Huge The indicator function :
$$\mathbb 1_A (x) = \begin{cases} 1\hspace{0.5cm} \text{if } x\in A\\ 0\hspace{0.5cm} \text{if } x\notin A \end{cases}$$\end{document}


The problem is that the command mathbb 1_Aor more specifically mathbb 1 returns a weird sign that almost resembles the indicator function :

Is there any package that I should add ? Thanks !

\documentclass{article}

\usepackage{amsmath}

\begin{document}
%>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
$\mathbf {1} _{A}(x):= \begin{cases}1~&{\text{ if }}~x\in A~,\\0~&{\text{ if }}~x\notin A~.\end{cases}$
%<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
\end{document}


• The output here is the number one in bold. I'm looking for the number one in the $\mathbb$ type, just like the real number set $\mathbb R$. – Hamdiken Feb 15 at 19:00
• The typography rule is bold. Follow the specified links upwards for blackboard fonts which are supposed to be used on blackboards and not for printed texts. – gigiair Feb 15 at 19:30