[O] LaTeX math doesn't always export to HTML as math

[Richard Stanton]

I created the following very simple org file:

————


#+TITLE: *Math example*

\[ w_j = \nu_j \prod_{l<j} (1-\nu_l), \]


————

This exports to LaTeX fine, but when I export to HTML, the equation comes out 
as plain text

<p>
\[ w_j = \nu_j \prod_{l<j} (1-\nu_l), \]
</p>

Am I missing something?

By the way, org-version gives

Org mode version 9.0.5 (9.0.5-elpa @ /Users/stanton/.emacs.d/elpa/org-20170210/)