What is the recursive formula for this arithmetic sequence -16,-7,2,11,

Hello from MrBillDoesMath!

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