# Summation notation for time series

I need to add together the results of a function for four consecutive years prior to the start of a project. The function is calculated for individual years. It is (10 × (A + B + C) ÷ D). Each year has a set of values for the variables A, B, C, D. So maybe it is something like

sum (n=1..4, (10 × (At-n + Bt-n + Ct-n) ÷ Dt-n))

whereby I mean t=0 is the point in time when a project starts and "n" is the number of years prior to t=0 and would be from 1 to 4. I attempted to use the plain text version of sigma notation (summation notation) above because using equation editors is difficult with voice recognition software. Would you please help me get my notation correct? I don't really know what I am doing… any assistance would be greatly appreciated.

We will use subscripts to denote the number of years prior to 2014, so that $B_3$ is the value of $B$ for the year 2011, etc.
The quantity we are interested in is $$\sum_{n=1}^410\frac{A_n+B_n+C_n}{D_n}$$