Math Question

I have a math equation I want to express correctly, but I have been out of college for 10 years and I’m a little rusty.

This is my attempt, but I’m not sure I have the series written correctly:

• n = number of steps an argument is removed from an idea, where a reason to agree is one step removed, but a reason to agree with a reason to agree is two steps. 
• A₁ = Number of reasons to agree (Count as 1 point each, towards the idea)
• D₁  = Number of reasons to disagree (Count as 1 point each, towards the idea)
• A₂ = Number of reasons to agree with reasons to agree or disagree with reasons to disagree (Count as 1/2 point each, towards the idea)
• D₂  = Number of reasons to disagree with reasons to agree or agree with reason to disagree (Count as 1/2 point each, towards the idea)
• and so on

I’m not sure I have enough summation symbols.  If I define A sub 1 as “Number of” can I leave out the extra summation symbols shown in this equation: