A little confusing, but....
Term number 1 2 3 4 5 6 7
3 7 15 27 43 63 87
Note that the 3rd term = previous term + 4 times the previous term number = 7 + 4(2) = 15
4th term = 15 + 4(3) = 27
5th term = 27 + 4(4) = 43
6th term = 43 + 4(5) = 63
7th term = 63 + 4(6) = 87
Notice something else.....the difference between terms is 4, 8, 12, 16, 20, 24
Just for the heck of it, what would be the 8th term ????