find next value using previous value

Hi All,

i have below table, my output should be a column which uses

Target previous row-(Target previous row*0.3863636363)

eg: 2019= 2019

2020= Target2019-(Target 2019*0.3863636363)

2021= Traget 2020-(Target 2020*0.3863636363)

i tried using below DAX formula but the value is only correct for 2020, as its using last nonblank value of year 2019 for finding growth_Target all the years which is not correct 

growth_Target =
IF(ISBLANK('Table'[Target]),
    VAR _curRank = 'Table'[Index]
    VAR _lastNonBlankRank = MAXX(FILTER('Table', 'Table'[Index]< _curRank && NOT ISBLANK('Table'[Target]) ), 'Table'[Index])
    VAR _lastNonBlankValue = LOOKUPVALUE('Table'[Target], 'Table'[Index], _lastNonBlankRank)
   RETURN
_lastNonBlankValue-( _lastNonBlankValue * POWER(0.3863636363, _curRank - _lastNonBlankRank)), 
    'Table'[Target])

can someone help what exactly is wrong