prop_isUnique :: Double -> Double -> Int -> Bool
prop_isUnique fstNum growthRate len = 
  let ss = seriesN fstNum growthRate len
  in ss == nub ss
prop_isUnique :: Double -> Double -> Int -> Bool
prop_isUnique fstNum growthRate len = 
  let ss = seriesN fstNum growthRate len
  in ss == nub ss
prop_isUnique fstNum growthRate len = 
  let ss = seriesN fstNum growthRate len
  in ss == nub ss