isomorphisms b = nub $ do
  b' <- [b,flipBoard b]
  b' : map (`rotateBoard` b') [1..5]
isomorphisms b = nub $ do
  b' <- [b,flipBoard b]
  b' : map (`rotateBoard` b') [1..5]
isomorphisms b = nub $ do
  b' <- [b,flipBoard b]
  b' : map (`rotateBoard` b') [1..5]