$\begin{array}{1 1} \bar{\gamma} = \frac{1}{R} \bigg[\large\frac{1}{2^2} -\frac{1}{n^2} \bigg]\;where \;n=3,4,5 ... \\ \bar{\gamma} = \frac{1}{R} \bigg[\large\frac{1}{3^2} -\frac{1}{n^2} \bigg]\;where \;n=4,5,6 ... \\ \bar{\gamma} = \frac{1}{R} \bigg[\large\frac{1}{4^2} -\frac{1}{n^2} \bigg]\;where \;n=5,6,7 ... \\ \bar{\gamma} = \frac{1}{R} \bigg[\large\frac{1}{1^2} -\frac{1}{n^2} \bigg]\;where \;n=2,3,4 ...\end{array} $