concatenate rows of values in a string

OK, if you want the results to appear in a single cell then you'll need some form of VBA to do this.

Copy the code below and paste it into a general module.

Function aconcat(a As Variant, Optional sep As String = "") As String


'VBA code by Harlan Grove
   
    Dim y As Variant
 
    If TypeOf a Is Range Then
        For Each y In a.Cells
            aconcat = aconcat & y.Value & sep
        Next y
    ElseIf IsArray(a) Then
        For Each y In a
            aconcat = aconcat & y & sep
        Next y
    Else
        aconcat = aconcat & a & sep
    End If
 
    aconcat = Left(aconcat, Len(aconcat) - Len(sep))


End Function

Assuming your data is in the range A2:A8, enter this array formula** in B2:

=SUBSTITUTE(TRIM(aconcat(IF(A2:A8=1," "&ROW(A2:A8)-ROW(A2)+1,"")))," ",", ")

** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.