What does the i after the sequence number in summation notation mean?

The "i" will be your starting point, from where you'll start adding the numbers.

Sigma notation or summation notation is a way used in mathematics, you might also call it a formula, used to shorty write systematical sums (that have a pattern in the summed digits).

→ The image below might be of great use and help.

Hope it helped,

BioTeacher101

pakistan's principal natural resources are arable land and water. about 25% of pakistan's agriculture accounts for about 21% [1] of gdp and employs about 43% of the labour force. in pakistan, the most agricultural province is punjab where wheat and cotton are the most grown.