Answer:

- All positive integers greater than 1 will be its domain.
Step-by-step explanation:
The explicit equation for an arithmetic sequence is,

Where,
= nth term in the arithmetic sequence,
= 1st term in the arithmetic sequence,
d = common difference.
Here, the first term of 5 and a second term of 3. So the common difference is -2.
Putting the values,

i.e 
As n neither be negative nor fraction, because it is the number of term, so all positive integers greater than 1 will be its domain.