Series and index number were (are) not important enough for the powers that be to include in the official list of metadata...at least in the ePub realm. I've heard that will be changed with the next iteration, whenever that happens to come out. In the meantime, Calibre has it's own set of metadata tags that include "calibre:series" and "calibre:series_index" you can add them in the .opf like this:
<meta content="Your Book #" name="calibre:series_index" />
<meta content="Your Series Name" name="calibre:series" />
Whether or not any reader/app actually notices them - or allows you to do anything with them is another matter. Marvin, and of course Calibre itself, allow full use of those tags.
Cheers!
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