Question

Pls answer as quickly as possible!!

Answer 1

I don't think any of the answer choices are right ...

Explanation:

Using induction (if you would like the steps included, please ask), we can show that
`a_n = \frac{1}{\tbinom{n+1}{2}}`. We can then simplify the given expression:

`(1)/(a_(1670))-1390187=\tbinom{1670+1}{2}-1390187 = 1395285-1390187=5098.`

Sorry, but that doesn't appear to be one of the answer choices