 Heptagonal number

The polygonal number $P_{7,n}=n(5n-3)/2$ for a positive integer $n$.

A heptagonal number is a figurate number that represents a heptagon (a seven-sided polygon). The formula for the \(n\)-th heptagonal number \(H_n\) is given by: \[ H_n = \frac{n(5n - 3)}{2} \] where \(n\) is a positive integer.