Public Function IsFibonacci(ByRef lNumber As Long) As Boolean
Dim i As Long 'anterior
Dim y As Long 'actual
Dim x As Long 'Restultado a checkear
i = 1
y = 1
    Do While x < lNumber
        x = i + y
        i = y
        y = x
        If x = lNumber Then IsFibonacci = True: Exit Function
    Loop
    IsFibonacci = False
End Function

Public Static Function IsFibonacciMrFrog(ByVal lngNumber As Long) As Boolean
Dim dblRaised                                       As Double
Dim dblSum                                          As Double
Dim dblSqr                                          As Double
 
    dblRaised = lngNumber * lngNumber
    dblSum = dblRaised + dblRaised + dblRaised + dblRaised + dblRaised + &H4
    dblSqr = Sqr(dblSum)
    IsFibonacciMrFrog = (dblSqr - CLong(dblSqr) = &H0)
    If IsFibonacciMrFrog Then Exit Function
    dblSum = dblSum - &H8
    dblSqr = Sqr(dblSum)
    IsFibonacciMrFrog = (dblSqr - CLong(dblSqr) = &H0)
End Function

Private Sub Form_Load()
Dim x           As Long
Dim s           As String
 
    For x = 0 To 100
        If IsFibonacciMrFrog(x) Then
            s = s & x & " "
        End If
    Next
    Debug.Print s
End Sub

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