If an=2na_n = 2^nan=2n is a solution, what is the recurrence relation?
an=2an−1a_n = 2a_{n-1}an=2an−1
an=an−1+2a_n = a_{n-1} + 2an=an−1+2
an=2an−1+1a_n = 2a_{n-1} + 1an=2an−1+1
an=an−1+2an−2a_n = a_{n-1} + 2a_{n-2}an=an−1+2an−2