How do I specify a task in org-mode as needing to be done 3 times a week without being specific about which day of the week it is?
Org-mode documentation for repeated tasks suggests the use of y/m/d/h intervals, but I didn't find the syntax for specifying an event n times per interval.
You can define your TODO as a habit in org:
The TODO may also have minimum and maximum ranges specified by using the syntax `.+2d/3d', which says that you want to do the task at least every three days, but at most every two days.
Maybe this would serve your purpose?