[ 1*x[2] + 1*x[3] = k[56],
  1*x[4] + 1*x[16] = k[57],
  1*x[5] + 1*x[15] = k[58],
  1*x[6] + 1*x[17] = k[59],
  1*x[7] + 1*x[8] = k[60],
  1*x[10] + 1*x[11] = k[61],
  1*x[12] + 1*x[13] = k[62],
  1*x[20] + 1*x[21] = k[63] ]