Hello from MrBillDoesMath!
Answer:
a(n) = -16 when n = 1
a(n) = a(n-1) + 9 when n > 1 ( i.e. n = 2,3,4)
Discussion:
First observation:
-16 + 9 = -7
-7 + 9 = 2
2 + 9 = 11
So the pattern seems to be gotten by addition of 9 to each number. The recursive formula therefore is this:
a(n) = -16 when n = 1
a(n) = a(n-1) + 9 where n > 1 ( i.e. = 2,3,4)
Thank you,
MrB