Notice that the formula expands to this. Then divide by 2. Drag the fill handle across the range that you want to.
In the Insert Sequence Number dialog box please click New button to expand this dialog box.
So the missing terms are 8 4 12 and 16 4 20. Check that the pattern is correct for the whole sequence from 8 to 32. Sure you can create a numbered list quickly enough but that feature works with additional text - youre. Select both the cells and drag the fill handle across the range that you want to fill.