IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
sum switch122122 1. n : 2. f : n 3. i : (n-1)
4. (i, i+1) nn sum(f(x+i) | x < 2)+sum(f((i, i+1)(x+2+i)) | x < n-i-2)
=
sum(f(x+i) | x < n-i)
By:
Subst' (sum(f((i, i+1)(x+2+i)) | x < n-i-2) = sum(f(x+2+i) | x < n-i-2)) 0