You can also do this using a macro. Here is one method.
To enter this Macro (Sub), alt-F11 opens the Visual Basic Editor. Ensure your project is highlighted in the Project Explorer window. Then, from the top menu, select Insert/Module and paste the code below into the window that opens.
To use this Macro (Sub), alt-F8 opens the macro dialog box. Select the macro by name, and RUN.
Option Explicit
Sub ReArrange()
Dim vSrc As Variant, rSrc As Range
Dim vRes As Variant, rRes As Range
Dim I As Long, J As Long, K As Long
Dim lColsCount As Long
Dim Col As Collection
'Upper left cell of results
Set rRes = Range("D1")
'Assume Data in A1:Bn with no labels
Set rSrc = Range("a1", Cells(Rows.Count, "A").End(xlUp)).Resize(columnsize:=2)
'Ensure Data sorted by index number
rSrc.Sort key1:=rSrc.Columns(1), order1:=xlAscending, key2:=rSrc.Columns(2), order2:=xlAscending, MatchCase:=False, _
Header:=xlNo
'Read Source data into array for faster processing
' compared with going back and forth to worksheet
vSrc = rSrc
'Compute Number of rows = unique count of index numbers
'Collection object can only have one entry per key
' otherwise it produces an error, which we skip
Set Col = New Collection
On Error Resume Next
For I = 1 To UBound(vSrc)
Col.Add Item:=vSrc(I, 1), Key:=CStr(vSrc(I, 1))
Next I
On Error GoTo 0
'Compute Maximum Number of columns in results
' Since there is one entry per Index entry, maximum number of
' columns will be equal to the Index that has the most lines
' So we iterate through each Index and check that.
For I = 1 To Col.Count
J = WorksheetFunction.CountIf(rSrc.Columns(1), Col(I))
lColsCount = IIf(J > lColsCount, J, lColsCount)
Next I
'Set up Results array
' Need to add one to the columns to account for the column with the Index labels
ReDim vRes(1 To Col.Count, 1 To lColsCount + 1)
'Now populate the results array
K = 1
For I = 1 To Col.Count
vRes(I, 1) = vSrc(K, 1)
J = 2
Do
vRes(I, J) = vSrc(K, 2)
J = J + 1: K = K + 1
If K > UBound(vSrc) Then Exit Do
Loop Until vSrc(K, 1) <> vRes(I, 1)
Next I
'Set the results range to be the same size as our array
Set rRes = rRes.Resize(rowsize:=UBound(vRes, 1), columnsize:=UBound(vRes, 2))
'Clear the results range and then copy the results array to it
rRes.EntireColumn.Clear
rRes = vRes
'Format the width. Could also format other parameters
rRes.EntireColumn.ColumnWidth = 10
End Sub