Hello, I'd be very grateful for help to identify a GENERAL equation or formula for our condominium reserve analysis: We have estimated the amount of $ needed in each of the next 50 years to pay for "capital replacements", like new roofs, etc. The projected needed $ amounts for some future years is low, but for some other future years is very high, for example, $45,000 five years from now, then down to $25,000 three years after that, then back up to $50,000 seven years after that ... up and down by very different amounts at various points-in-time that are NOT evenly spaced, e.g., yearly intervals of 3, 5, 7, 3, 5, 2, 7, 3, etc.

What is a GENERAL formula to determine the amount of $ that must be saved in each of the next 50 years in order to ensure that enough $ will be on-hand at each future year when a pre-determined estimated $ amount will be needed?

I'm thinking there could be TWO different formulas:

One that keeps the annual required $ saved amount CONSTANT throughout the entire 50-year period,

and a different formula that allows the annual required $ amount to be saved to be changed (up OR down) at desired future years, for example: if we wanted the required annual $ amount being saved to be increased by 5% in each successive year rather than keeping it constant, OR alternatively, if we wanted to SKIP saving any amount in certain years, etc.

Thank you very much for any help !! SteveCHOCC