How can I show formatted math expressions in Bitbucket or github markdown?
This feature is highly requested and have been under development for years now. There does not seem to be a decent solution for it yet.
Formatted math is supported in reStructuredText and I can use it as a last resort. But as markdown gains popularity I would rather stick to it than use yet another markup language.
Bitbucket's (and GitHub's) Markdown does not currently support formatted math expressions. A good workaround I discovered that works with both is to use codecogs to convert my LaTeX math expression into a hosted image and use its URL to embed it in my Markdown document.
Go to codecogs and enter your LaTeX equation in the text box.
\zeta(s) = \sum_{n=1}^\infty \frac{1}{n^s}
Right click the Click here to Download Image (GIF) link shown under the text box and copy the link's address. Then, embed the URL in your markdown document as an image:

The image should show in your formatted Markdown document like:
This method also works with GitHub and any Markdown processor that supports externally hosted images.
Also, mathURL offers a similar service and a nice interface but does not support https (can't use with GitHub).