[EUV071STR48]

Thanks, that's about what I suspected right after posting ('something like log-function'). But does it have to be?

The more I think about it, there's quite a wide range of data sets I can create from my initial rule. The daily increase is not limited, so it should be possible to create almost every kind of graph, as long as it increases. Truely a noob question I came up with, if I don't overlook something again...