Sigma Summation function in Excel - Aritmetical Gradients-CodePudding

I want to write a formula in Excel that works as follow:

Where:

G = Aritmetical Gradient value 
R = Rent value
i = Interest Rate value (expressed in %)
n = Numbers of months

Any help you can give me, I will be really thankful.

CodePudding user response：

SUMPRODUCT will do this:

=SUMPRODUCT((B2 B1*(B4-SEQUENCE(B4 1,,0)))*(1 B3)^SEQUENCE(B4 1,,0))

I made the assumption you want to include where k=n if not then remove the 1s in the formula.

If one does not have SEQUENCE we can substitute (ROW($ZZ1:INDEX($ZZ:$ZZ,B4 1))-1)

=SUMPRODUCT((B2 B1*(B4-(ROW($ZZ1:INDEX($ZZ:$ZZ,B4 1))-1)))*(1 B3)^(ROW($ZZ1:INDEX($ZZ:$ZZ,B4 1))-1))