So since 7 is the second term, we multiply 2 by 4 and add it to 7. We get 15
Our sequence so far: 3,7,15,
Then we multiply 4 and 4 to get 16 as 15 is the FOURTH term then add 16 to 15. We get 31.
Do you notice a pattern? 3,7,15,31.
Yes 2n+1 can represent each change for the terms.
So we keep calculating...