Exactly

Not at all, that's exactly where I 'found' it

As I replied to TheChaz, I only included them all for completeness sake, in case I had overlooked something. It appears I hadn't

Again, you are quite right, nothing at all wrong with that

My problem was with the result I was getting at x=31622777, but as I updated, it turns out that Excel can't count and I can't read. I had the equations set up in Excel so it would indicate for a given x, y and z if they were all true. In this particular instance I took it on blind faith that it was correctly reporting one or more of them was false so looked to the equations for a reason. If I'd had the sense to look at Excel's output for the individual equations, I would have noticed that (31622777)² couldn't end with a zero

Thanks,

Pro