map length (tiers :: [[ Map Nat2 Nat2 ]])  =  [1,1,2,2,2,1]

length (list :: [ Map Nat2 Nat2 ])  =  9

allUnique (list :: [ Map Nat2 Nat2 ])  =  True

ratioRepetitions (list :: [ Map Nat2 Nat2 ])  =  0 % 1

tiers :: [Map Nat2 Nat2]  =
  [ [Map []]
  , [Map [(0,0)]]
  , [ Map [(0,1)]
    , Map [(1,0)]
    ]
  , [ Map [(1,1)]
    , Map [(0,0),(1,0)]
    ]
  , [ Map [(0,0),(1,1)]
    , Map [(0,1),(1,0)]
    ]
  , [Map [(0,1),(1,1)]]
  ]