Answer:
The nth term: an = 27(1/3)^(n-1).
Also see below.
Explanation:
Each term after the first is obtained by multiplying the previous term by 1/3.
It is a geometric sequence with first term 27 and common ratio 1/3.
The formula for the nth term an is an = 27(1/3)^(n-1).
If you want the sigma notation formula for the sum of n terms of this series it is :
n
∑ 27(1/3)^k This gives the sum of the first n terms.
k=0