V_j (j=0..4):
  V_0 = [[4, 5, 1, 1, 5, -2], [2, -2, -5, 3, 1, 0]]
  V_1 = [[3, -5, -6, 0, 1, -1], [-5, 0, 1, 0, -5, -4]]
  V_2 = [[-2, 3, 0, -2, 0, -1], [0, -3, -1, -1, 1, -6]]
  V_3 = [[5, 1, 2, -5, -1, -4], [1, -1, 3, 4, -1, -6]]
  V_4 = [[3, -2, -1, 6, -1, -2], [0, -5, 2, -2, 2, -2]]
Q(y) = sum_{a<b<c<d} mu_abcd * Pf_abcd(y),  Pf_abcd = y_ab y_cd - y_ac y_bd + y_ad y_bc  (indices 1..6):
  mu = {'1234': -1, '1236': 1, '1245': -1, '1246': -2, '1256': 1, '1456': -2, '2346': 1, '2356': 1, '2456': -1, '3456': -1}
