Which expression represents ana_nan for an=an−1+2a_n = a_{n-1} + 2an=an−1+2 with a0=0a_0 = 0a0=0?
an=2na_n = 2nan=2n
an=n+2a_n = n+2an=n+2
an=2na_n = 2^nan=2n
an=n2a_n = n^2an=n2