Well it looks like it is harder to get to the top of the iTunes U mathematics Top Collections! See https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewTop?cc=gb&genreId=40000077&popId=36 (which should cause iTunes to open and display the list).
Looking at where my own iTunes U albums come in that list, my Functional Analysis album is currently 36th, Mathematical Analysis is 56th, Advanced Mathematics is 62nd, but Foundations of Pure Mathematics looks to be catching up (currently 71st).
I guess that it will be hard to match singingbanana (I mean Quite Easily Done)!
However, if you actually search for Pure Mathematics in the iTunes store, very few collections show, and most of the iTunes U Episodes showing are mine. I’m not sure what that means!