Copy visible cells from Row B paste to Row A in filter mode

Hi Experts,

I have query regarding visible cells macro. I need copy the formula from A20 to used range from B and paste visible cells from Row A20. Could you please help me regarding this. I have attached below codings.

'Getting value from range B to A using Trim
Range("B20").Select
Selection.Copy
Range("A20").Select
ActiveCell.FormulaR1C1 = "=TRIM(RC[1])"
Could you please provide codings copy the formula from A20 to used range from B and Paste visible cells from A20 to till Range "B" data availability?
Range("B20").Select
Selection.End(xlDown).Select
Range("A15844").Select ' last row should find based B data availability (it should not stop A15844 data may increase or decrease)
Range(Selection, Selection.End(xlUp)).Select
Range("A20:A15844").Select
Range("A15844").Activate
Selection.SpecialCells(xlCellTypeVisible).Select
ActiveSheet.Paste
Application.CutCopyMode = False
Selection.AutoFilter
Columns("A:A").Select
Range("A15512").Activate
Selection.Copy
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False

Thanks in advance
Lakshmipathi