1. ## Infinite series

Assume the nth partial sum of the series $\displaystyle \sum^{\infty}_{n=1} a_n$ is the following:

$\displaystyle s_n: 2-n3^{-n}$

a) Find $\displaystyle a_n (n>1)$

$\displaystyle a_n = ?$

2. $\displaystyle a_n = s_n - s_{n-1}$