1, 3, 10, 21, 64, 129, 356, 777

Question:
1, 3, 10, 21, 64, 129, 356, 777

[A].

10

[B].

21

[C].

64

[D].

129

Answer: Option E

Explanation:

A x 2 + 1, B x 3 + 1, C x 2 + 1, D x 3 + 1 and so on.

So, 356 is wrong.