Sum of the following series to `n` term: `\ 1+3+6+10+15+.............`

Explanation

To find the sum of the series \( S_n = 1 + 3 + 6 + 10 + 15 + \ldots \) up to \( n \) terms, we can follow these steps:

### Step 1: Identify the Pattern
The terms in the series are known as triangular numbers. The \( n \)-th triangular number \( T_n \) can be expressed as:
\[ T_n = \frac{n(n + 1)}{2} \]
This means:
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