I can't find the topic I made.. ugh.
Any way I'm trying to prove always ends in the digits .
I almost had it.. something like:
. . . this doesn't quite work. I have to tweek that somehow to show it.
Anyone? I know the proof is similar to what I have. I just can't tweek it to get integers x = 1, 2, ... to satisfy that and include all the powers of 5 to show that you get something (something like 1000 + 100 + 25) and hence will always have 00 + 25 which completes the proof.