Vector magnitude notation $\|$ cannot be rendered in markdown table.

[tengjuilin]

Hello, I am trying to display the vector magnitude notation $|$ in a table using markdown. For example, the magnitude of velocity vector $|v|$. It can be rendered properly in jupyter notebook; however, it cannot be rendered properly in the nbviewer. Could you help me out? Project with problem: OrbitSimulation, very last section of list of variables Example:

|`v`|list|$\|\mathbf{v}\|$|$\mathrm{m/s}$|The magnitude of $\mathbf{v}$|

Thanks!

Describe the bug The vector magnitude notation $\|$ cannot be rendered correctly in a table using markdown.

To Reproduce Steps to reproduce the behavior:

1. Go to 'OrbitSimulation - Github' or 'OrbitSimulation - nbviewer'
2. Scroll down to 'Rocket Variables' (the very end of the project)
3. See error: notation displayed incorrectly

Expected behavior Render of the vector magnitude notation "double vertical lines". ||v|| Desired render example from jupyter notebook:

Screenshots Undesired render from nbviewer: Undesired render from Github:

Desktop (please complete the following information):

• OS: [Windows 10 1803]
• Browser [Firefox; Chrome]
• Version [64.0; 66.0.3359.139]