Calculate angle between points

[hannibal smith]

I've an array with values, I need to calculate the angle between them, like in picture, assuming the increment of x is always 1

So i tryed:

 Const Rad2Deg As Double = 180.0 / Math.PI
   Const Deg2Rad As Double = Math.PI / 180.0
   Dim newlist As New List(Of UShort)
 
        For i = 0 To MySourceArray.Length - 1 Step 1
          Dim first As UShort = MySourceArray(i)
          Dim second As UShort = MySourceArray(i + 1)
            Dim angle = Math.Atan2(first - second, 1) * Rad2Deg
            newlist.Add(angle)
        Next

Some data for the arrays:

  &H2020,&H 4544,&H4331,&H372E,&H434F,&H4D20,&H2020,&H2020

but I get overflow exception at the line where Atan2 is calculated. But if I try to do the the calc manually the result seem ok.
What am I missing?