If the sum of the first nnn terms of a sequence is Sn=3n−1S_n = 3^n - 1Sn=3n−1, find the nnn-th term ana_nan.
an=2⋅3n−1a_n = 2 \cdot 3^{n-1}an=2⋅3n−1
an=3na_n = 3^nan=3n
an=3n−1a_n = 3^{n-1}an=3n−1
an=2⋅3na_n = 2 \cdot 3^nan=2⋅3n