If $$\left\{a_n\right\}_{n - 1}^{\infty}$$ is such that $$a_1 = a_2 = 1$$ and $$a_k = a_1 + a_2 + ......... + a_{k - 1}$$ for $$k \geq 3$$, then $$a_7 =$$

A

16

B

32

C

64

D

128