A few years ago, just for fun, I enrolled in a UCLA extension course on Measure Theory: <a href="https:&#x2F;&#x2F;uclaextension.edu&#x2F;pages&#x2F;Course.aspx?reg=Z5529" rel="nofollow">https:&#x2F;&#x2F;uclaextension.edu&#x2F;pages&#x2F;Course.aspx?reg=Z5529</a><p>It stretched my brain in ways that my day job doesn&#x27;t.  I&#x27;ve since continued to take all of the courses in the series, which are always about &quot;interesting&quot; mathematics.  The professor (Dr. Michael Miller) has been teaching these graduate-level extension courses for something like 20+ years.  If you are in the area of UCLA, I highly recommend attending.  Sadly, there&#x27;s no online option, so you&#x27;ll have to be a local.<p>More info on the course from another student (and clear fan): <a href="http:&#x2F;&#x2F;boffosocko.com&#x2F;2015&#x2F;09&#x2F;22&#x2F;dr-michael-miller-math-class-hints-and-tips-ucla-extension&#x2F;" rel="nofollow">http:&#x2F;&#x2F;boffosocko.com&#x2F;2015&#x2F;09&#x2F;22&#x2F;dr-michael-miller-math-clas...</a>