How to do a bold 1 (\mathbbm{1}) in MathJax
mathjax
Solution
You can use Unicode characters directly, e.g., ``, or via the non-standard macro `\unicode{x1D7D9}`.
Both of these can be used in macro definitions as well, cf. http://docs.mathjax.org/en/latest/tex.html#defining-tex-macros.
Problem
I'm looking for blackboard bold numerals in LaTeX displayed with MathJax. It seems that the `\mathbbm` command is not (yet) available from MathJax (as said in the documentation). Is there anyway to have support for the `\mathbbm` command, e.g., to have nice bold 1 ? I tried to load an extension, or trick from this question, but nothing works. Here is an example showing the failure: with makebigmaths. It seems to be a known and old issue of MathJax, coming from a font limitation. And no third party extensions seem to solve it. However, Jupyter notebooks supports it in its Markdown cells.