Hi

Can any one help me understand what I am doing wrong. My exam is approaching real fast so would really apprecaite ur help. The link to the actual question is copied below

https://www.beatthegmat.com/ps-t6322.html

Here is what I did

The 5th term in the series is 1 (i.e 5-4)
the 6th term is 2 (i.e 6-4)
The 97th terms is 93

So essentially from the 5th term in the series to the 97th term we have a series of consequitive integers from 1 to 93

So the sum of all consequitive integers from 1 to 93 inclusive =

(94/2) * (94-1+1) = 4418

Now the sum of the first 4 numbers in the sequence is (2 + (-3) + 5 + (-1) ) = 3

So sum of first 97 terms is 4418 + 3 = 4421

This is obviously wrong, but I dont know why. Please Help.

Thanks in advance