Факториал для уравнения - VB

Формулировка задачи:

Здравствуйте! Прошу помощи. Найдите факториалы в натуральных числах: a!+b!+c!=d! Где моя ошибка?

Option Explicit
 
Private Sub Command1_Click()
Dim a As Integer, b As Integer, c As Integer, d As Integer, k As Integer
For a = 1 To 100
  For b = 1 To 100
    For c = 1 To 100
      For d = 1 To 100
      If a ! + b ! + c ! = d ! Then
      k = k + 1
      Text1 = Text1 & k & ") a = " & a & "; b = " & b & "; c = " & c & "; d = " & d & vbCrLf
      End If
      Next
    Next
  Next
Next
 
End Sub

Решение задачи: «Факториал для уравнения»

textual
                            Листинг программы 
                        

                            Option Explicit
 
Private Sub Command1_Click()
    Dim a As Integer, b As Integer, c As Integer, d As Integer, k As Integer
    Dim x() As Long, n As Integer, i As Integer
    n = 12
    ReDim x(1 To n)
    For i = 1 To n
       x(i) = f(i)
    Next i
    Text1.Text = ""
    For a = 1 To n
      For b = 1 To n
        For c = 1 To n
          For d = 1 To n
            If x(a) + x(b) + x(c) = x(d) Then
              k = k + 1
              Text1.Text = Text1.Text & k & ") a = " & a & "; b = " & b & "; c = " & c & "; d = " & d & vbCrLf
              'Text1.Text = Text1.Text & "    a! = " & x(a) & "; b! = " & x(b) & "; c! = " & x(c) & "; d! = " & x(d) & vbCrLf
              'DoEvents
            End If
          Next
        Next
      Next
    Next
    MsgBox k
End Sub
 
Function f(n)
  If n = 1 Then f = 1 Else f = f(n - 1) * n
End Function
                        