Sum of the following series to `n` term: `1+3+7+13+21+ ............`

Explanation

To find the sum of the series \( S_n = 1 + 3 + 7 + 13 + 21 + \ldots \) up to the \( n \)-th term, we first need to analyze the pattern in the series.

### Step 1: Identify the pattern in the series
Let's observe the terms:
- The first term is \( 1 \).
- The second term is \( 3 \).
- The third term is \( 7 \).
- The fourth term is \( 13 \).
...