How to do a bold 1 (\mathbbm{1}) in MathJax

Question

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.

Answer 1

You can use Unicode characters directly, e.g., 𝟙, 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.