If an=an−1+3a_n = a_{n-1} + 3an=an−1+3 and a0=0a_0 = 0a0=0, what is the closed form of ana_nan?
an=3na_n = 3nan=3n
an=n+3a_n = n + 3an=n+3
an=3na_n = 3^nan=3n
an=n3a_n = n^3an=n3