Arithmetic Sequence

The explicit formula for arithmetic sequences always follows a specific format. The xth term aᵪ is always equal to the first term a₁ plus the common difference d (x - 1) times:

aᵪ = a₁ + d(x - 1)

In your particular problem,

first term = a₁ = 16

common difference = d = ?

The numbers in your list don't have a consistent common difference.

16 - 15.5 = 0.5

15.5 - 14 = 1.5

14 - 13.5 = 0.5

Unfortunately, no common difference means no arithmetic sequence. No explicit formula exists for the numbers in the list as given.