A sequence can be generated by using the equation shown, where a1 = 12 and n is a whole number greater than 1

an = 1.5 + a(n-1)
What are the first four terms in the sequence?

12
13.5
16
19.5

12
13.5
15
16.5

12
13.5
16.5
21

12
13.5
15.5
18