BBM numerals with Texpad's internal typesetter
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The bbm package used to write double stroked numerals common in many mathematics and physics papers uses “bitmapped fonts”, an old technology we have deprecated in Texpad’s internal TexpadTeX typesetting engine.

Why?

A bitmapped font specifies a character as an array of solid squares. These do not scale smoothly as you zoom, and they are not compatible with modern antialiasing techniques. Consequently, they do not display at the same high quality that TeX users are used to, and they have been deprecated both in and outside the TeX world in favour of vectored fonts, which look great at any size.

What is the replacement

Although it works with TexpadTeX, these numerals can be rendered with high quality, modern vectored fonts via the dsfonts package. For example:

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