At 04:41 PM 6/24/2005, Max wrote: >Note that >sum(i=1 to x) i-phi(i) = x*(x+1)/2 - sum(i=1 to x) phi(i) > >So if x divides sum(i=1 to x) phi(i) and (x+1)/2 is integer (i.e., x is >odd), then >x divides sum(i=1 to x) i-phi(i) as well. OK, it was something simple. Thank you!