Answer:
216
Step-by-step explaination
They are cubic numbers.
In the sequence;
if you cube 1, you get 1.
if you cube 2, you get 8.
if you cube 3, you get 27.
if you cube 4, you get 64.
if you cube 5, you get 125.
So if you cube 6, you get 216 and thus you're answer