Claus,

Here is my understanding of the math, manually done.

Let#s say we set first 4 rows of n as 1,2,3,4.
Let's say we set first 4 rows of w as 10.20,30,40

When n = 1, computation does not exist (?)
When n = 2, f(2) = 10 x e^(-1) = 3.678
When n = 3, f(3) = 10 x e^(-2) + 20 x e^(-1) = 8.711
When n = 4, f(4) = 10 x e^(-3) + 20 x e^(-2) + 30 x e^(-1) = 14.240


The formula you provided starting with row 2 is :
$B$4*SUMPRODUCT(D2*(EXP(-1*(ROW(INDIRECT($A$2&":"&C2))-1)/$B$3)))


This gives me

f(1) = 10
f(2) = 27.35758882
f(2) = 45.09644173
f(4) = 62.12007171


See the difference? Thank you.


On Thursday, April 26, 2018 at 7:21:50 AM UTC+1, Claus Busch wrote:
Hi Ron,

Am Wed, 25 Apr 2018 13:46:11 -0700 (PDT) schrieb Ron George:

Thanks a lot. I put the "C2-1" bit there make it understand that the upper limit of sigma function is n-1 where n is the day on any row. If n = 3, C2-1 = 1.

Also, do you think my formula as a whole is correct?

my understanding for your formula is a bit different.
Have a look:
https://1drv.ms/x/s!AqMiGBK2qniTgcxMl0ftNOJuVY6Duw


Regards
Claus B.
--
Windows10
Office 2016