{ diff(x1, t) = 0,
  diff(x2, t) = 0/k17,
  diff(x3, t) = (1*k5*x4*x7 + (-1)*(k15*x3 - k3*k21*x6) + (-1)*k12*x3*x9 + (-1)*k14*x3)/k17,
  diff(x4, t) = ((-1)*k5*x4*x7 + 1*(k3*k21*x5 - k4*x4) + 1*k14*x3 + 1*k14*x10 + 1*k14*x11)/k17,
  diff(x5, t) = ((-1)*(k6*x7*x5 - k7*x6) + 1*(k1*k21*x8 - k2*x5) + (-1)*(k3*k21*x5 - k4*x4) + 1*(k7*x13 - k6*x16*x5) + 1*k14*x6 + 1*k14*x12 + 1*k14*x13)/k17,
  diff(x6, t) = (1*(k6*x7*x5 - k7*x6) + 1*(k15*x3 - k3*k21*x6) + 1*k13*x12 + (-1)*k14*x6)/k17,
  diff(x7, t) = ((-1)*k5*x4*x7 + (-1)*(k6*x7*x5 - k7*x6) + 1*k13*x17 + (-1)*k14*x7)/k17,
  diff(x8, t) = (-1)*(k1*k21*x8 - k2*x5)/k17,
  diff(x9, t) = ((-1)*k12*x3*x9 + 1*k13*x12 + 1*k13*x17 + 1*k14*x17 + 1*k14*x16 + 1*k14*x12 + 1*k14*x13 + 1*k14*x10 + 1*k14*x11)/k17,
  diff(x10, t) = (1*k12*x3*x9 + (-1)*(k15*x10 - k3*k21*x12) + (-1)*(k8*x10*x2/(x10 + k9) - k11*x11/(x11 + k10)) + (-1)*k14*x10)/k17,
  diff(x11, t) = ((-1)*(k15*x11 - k3*k21*x13) + 1*(k8*x10*x2/(x10 + k9) - k11*x11/(x11 + k10)) + (-1)*k14*x11)/k17,
  diff(x12, t) = (1*(k15*x10 - k3*k21*x12) + (-1)*k13*x12 + (-1)*(k8*x12*x2/(x12 + k9) - k11*x13/(x13 + k10)) + (-1)*k14*x12)/k17,
  diff(x13, t) = (1*(k15*x11 - k3*k21*x13) + 1*(k8*x12*x2/(x12 + k9) - k11*x13/(x13 + k10)) + (-1)*(k7*x13 - k6*x16*x5) + (-1)*k14*x13)/k17,
  diff(x14, t) = (-1)*(k18*(x3 + x10) + k19*(x13 + x16) + k20*x11)/k17,
  diff(x15, t) = 1*(k18*(x3 + x10) + k19*(x13 + x16) + k20*x11)/k17,
  diff(x16, t) = ((-1)*k11*x16/(x16 + k10) + 1*(k7*x13 - k6*x16*x5) + (-1)*k14*x16)/k17,
  diff(x17, t) = (1*k11*x16/(x16 + k10) + (-1)*k13*x17 + (-1)*k14*x17)/k17,
  diff(x18, t) = 1*k14*x7/k17,
  diff(x19, t) = (1*k14*x3 + 1*k14*x6)/k17,
  diff(x20, t) = (1*k14*x17 + 1*k14*x16)/k17 }