/sci/ - Science & Math

I was bying new weights for my barbell and it made me think of a fun /sci/ problem.

Let's say that you want to have N different combinations of weights that you can use on a barbell. And you also want to have the weights to increase by constant amount. In other words, if you arranged all the weight combinations in order, they would increase by constant amount (x kilos, x+y kilos, x+2y kilos, x+3y kilos, etc).

What is the minimum amount of plates that you need in order to fulfill these conditions?