Insertion de lignes dans une colonne

Option Explicit
'------------------------------------------
Sub inserer_2lignes()
Dim Maxi As Integer
Dim T_out() As Integer, Cptr As Integer, Lig As Integer

    Application.ScreenUpdating = False
    
    Maxi = Application.Max(Columns("A"))
    ReDim T_out(1 To Maxi * 3)
    Cptr = 1
     For Lig = 1 To Maxi
        T_out(Cptr) = Lig
        T_out(Cptr + 1) = Lig
        T_out(Cptr + 2) = Lig
        Cptr = Cptr + 3
     Next
    Range("A1").Resize(UBound(T_out), 1) = Application.Transpose(T_out)
End Sub