CAS Exam 7 - Mack 1994 - Standard Error for total reserve


I am having problem calculating the S.E for the total reserve, and I think I am applying the formula wrong. The formula for it should be :

So, for the following triangle:


Would the S.E for the reserve be:

Would it be:
1000+2000+3000+4000+ 2*(230)(190+200+210+220)

10*(1/(150+160+170+180) +
11*(1/(160+170+180) +
12*(1/(170+180)) +

I don’t understand how you have a little i subscript outside of summation on the RHS when there is no free index on the LHS. Are you sure this formula is correct?

If you look at the source (page 120), LHS does not have the subscript i neither. I think it is because it is not simply a sum of the individual years? I assume you are talking about the Ri?

Is my application of the Mack formula correct?