Private Sub Worksheet_Activate()
Dim n&, t, i&
With Sheets("Feuil1")
If .FilterMode Then .ShowAllData
n = .Cells(.Rows.Count, "a").End(xlUp).Row
t = .Range("a1:a" & n)
End With
ReDim r(1 To 2 * n, 1 To 1)
For i = 1 To UBound(t): r(2 * i - 1, 1) = t(i, 1): Next
Sheets("Feuil2").Columns(1).Clear
Sheets("Feuil2").Range("a1").Resize(UBound(r)) = r
End Sub