Hi, Try this.
List in column "A", as yout post.
Results in column "B" as required.
Dim Nst As String, Fst As String, Diff As Integer, nu As Integer
Dim cl As Range, AllNu As String

For Each cl In Range(Range("A1"), _
    Range("A" & Rows.Count).End(xlUp))
   If IsNumeric(cl.Value) Then
     On Error Resume Next
    Fst = cl.Value

    Nst = cl.Offset(1, 0).Value
    
    If Val(Nst) > Val(Fst) Then
        If Not Val(Nst) = Val(Fst) + 1 Then
            Diff = Val(Nst) - Val(Fst)
    End If
         For nu = 1 To Diff - 1
              Val (Fst) + nu
                AllNu = AllNu & Val(Fst) + nu & ","
            Next nu
  cl.Offset(0, 1).Value = Left(AllNu, Len(AllNu) - 1)
       End If
    End If
AllNu = ""
Diff = 0
Next cl
Regards Mick