Answer:
3, 12, 48, 192, 768, 3072, 12288 these are the next seven numbers
Add them all up and you get
= 16383 Answer C
Explanation:

So from 3 to 12 is multiply by 4
So we have checked that it works for all of them
Rule:
Each term is: Two to the power of the number3/4 times the number squared plus 0 times the number
I hope this has helped :)