Repeating as Ebbinghaus curve
 

Repeating function of Omnifocus is good enough. However, it would be better if it can add a repeating method as Ebbinghaus forgetting curve.
It'll be useful for students to review their knowledge.

Funny you should ask about this; I'd never seen such a request in years of reading everything posted here, and suddenly two such posts come along in the course of a week or two. I wrote a script to schedule such repeats, which you can find in [URL="http://forums.omnigroup.com/showthread.php?p=120577#post120577"]this thread[/URL]. Thanks for telling me the name!