Chapter 1.4, Problem 4P

For the following series, write formulas for the sequences a_n, S_n, and R_n, and find the limits of the sequence as $n\to \infty$ (if the limits exist).

${\displaystyle \underset{1}{\overset{\infty }{\sum }}{e}^{-n1n3}}$ Hint: what is $e^{-n1n3}$