So I have a simple budgeting idea where I save N amount per week, and I add n again to what I save next week, and so on and so forth.
So on the first week lets say I save 4. Next week I save 8, and then 12, and then 16 etc etc. And I want to do this for let's say 52 weeks for a year.
What formula should I use to solve for how much I need to save on the 31st week?
formula for sum of an AP is $S_n=\frac n2(2a+(n−1)d)$ here $n=52, a=4, d=4$