code: def    syd(c, s, l):
      
      return [(c-s) * (x/(l*(l+1)/2)) for x in range(l,0,-1)]
docs: This accountancy function computes sum of the years
      digits depreciation for an asset purchased for cash
      with a known life span and salvage value.  The depreciation
      is returned as a list in python.
      c = historcal cost or price paid
      s = the expected salvage proceeds
      l = expected useful life of the fixed asset
      Example: syd(1000, 100, 5)