Find the sum of `n` terms of the series `1.3.5.+3.5..7+5.7.9+...`

Explanation

To find the sum of the first `n` terms of the series `1.3.5 + 3.5.7 + 5.7.9 + ...`, we need to identify a general term for the series and then sum it up.

### Step-by-Step Solution:

1. **Identify the General Term**:
The series consists of products of three consecutive odd numbers. The first term is `1 * 3 * 5`, the second term is `3 * 5 * 7`, and the third term is `5 * 7 * 9`. Observing this pattern, we can express the `n`-th term, \( T_n \), as:
\[
T_n = (2n - 1)(2n + 1)(2n + 3)
...