Попробуйте:
Sub qwerty()
Dim s As String
Dim A2 As Range
Set A2 = Range("A2")
s = "In the sequence 1, 4, 9, 16, 25, ... each term is a perfect square. The first term is is 12, the second term is 22, and so on. A general formula for the nth term of the sequence is un=n2."
A2 = s
A2.Characters(Start:=92, Length:=1).Font.Superscript = True
A2.Characters(Start:=115, Length:=1).Font.Superscript = True
A2.Characters(Start:=158, Length:=1).Font.FontStyle = "Italic"
A2.Characters(Start:=185, Length:=1).Font.Subscript = True
A2.Characters(Start:=188, Length:=1).Font.Superscript = True
End Sub
![enter image description here](https://i.stack.imgur.com/Addyh.png)
Форматирование Character
соответствует стандартам VBA, а не тегам латекса или html.