The domain of a function is the set of values where the function is defined (values of x where y is defined).
The range of a function are the values of the function where is defined (values of y).
For the given function:

Domain: values of n {6,-8, 4, 2}
Range: values of k(n)
n= 6

n=-8

n=4

n=2

Then, the range is: {-16, 26, -10, -4}