Quelque chose

    Function MemFibonacci(ByVal n As Double) As Double
        If Nonexistent(n) Then
            Select Case n
                Case Is <= 1
                    MemFibonacci = n
                Case Else
                    MemFibonacci = MemFibonacci(n - 1) + MemFibonacci(n - 2)
            End Select
        Else
            Return MemFibonacci
        End If
    End Function