Which recurrence relation describes the sequence 2,4,8,16,…2, 4, 8, 16, \dots2,4,8,16,…?
an=2an−1a_n = 2a_{n-1}an=2an−1
an=an−1+2a_n = a_{n-1} + 2an=an−1+2
an=an−12a_n = a_{n-1}^2an=an−12
an=an−1+na_n = a_{n-1} + nan=an−1+n