Presently trying to model a clicker game where the cost increases 0.03% each time something is bought. I think this will ultimately not matter at large enough numbers, but I have no idea how to squeeze in that I need to take the ceiling at every step because, well, the first couple of purchases are 5/6/7 not 5/5.15/5.3045.

Currently the formula I'm using is:

=CEILING(SERIESSUM(1.03,0,1,INDEX(C3*SIGN(ROW(INDIRECT("1:"&(C9-C8)))))))

Row 3 being cost, row 8 being the current level (i.e. 252), row 9 being the next milestone (i.e. 500).

I'm sure that I could create some sort of abomination involving hard-coding values for each generator that matters and then cutting back to the formula when there's no noticeable effect by the lack of rounding, or I could just deal with the fact that my numbers are up to 20% lower at lower values, likely secure in the knowledge that it will result in few inefficiencies that matter... But I don't quite want to hack it that way.