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)

def    syd(c, s, l):
    """ 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)
    """
    return [(c-s) * (x/(l*(l+1)/2)) for x in range(l,0,-1)]