The sequence is .

The first term is .

The nth terms is .

The (n1)th terms is .

Then difference d = .

d = 4 − 2n − 2 + 2n

d = 2n − 2n + 4 − 2

d = 2

The value of difference d = 2.

First four terms are 2 , 0 , − 2 , − 4.