When we substitute the initial values of i, we find that the series is:
3, 5, 7, 9 ...
This means it is an arithmetic progression with the first term being 3 and the common difference being 2. We have to find the sum of the first 18 terms. Using the formula:
Sn = n/2[2a + (n - 1)d]
S₁₈ = 18/2[2(3) + (18 - 1)2]
S₁₈ = 360