A sequence can be generated using an-3a(n-1) where a1-6 and n is a whole number greater than 1. What are the first four terms of this sequence?

6,9,12,15
6,18,54,162
6,12,18,24
6,36,216,1296

The correct sequence is 6, 18, 54, 162. Let's test it with the formula:

a(n) = an-3a(n-1)
a(2) = 2-3a(1) = 2 - 3*6 = -16
a(3) = 3-3a(2) = 3 - 3*18 = -51
a(4) = 4-3a(3) = 4 - 3*54 = -156

Therefore, the first four terms of this sequence are 6, 18, 54, 162.