I was reading circular convolution topic from Digital Signal Processing Using Matlab 3rd Ed,by Proakis. I came across a strange term/symbol; I have highlighted it in attached snapshot
Update:Pg150; same chapter,same book(just before example 5.4) contains this notation and mentions that it is a rectangular window of length N
I have also attached snap of eq 5.24,in 2nd snap, where this RN(n) symbol appears also: