Find the pth term !

The sum $S_n$ of the first $n$ terms of an arithmetic progression is given by $S_n= \dfrac{n}{4}(13 + 7n)$ . The $p$ th term of the series is a multiple of the first term. Given that $p \ne 1$ , find the least possible value of $p$ .

Hints: Try to find out the following first:

• The first term of the series
• The $x$ th term of the series
• The series itself, note that the formula is for the sum
• The common difference