[ Eq(Derivative(x1, t), 0),
  Eq(Derivative(x2, t), 0),
  Eq(Derivative(x3, t), 0),
  Eq(Derivative(x4, t), 0),
  Eq(Derivative(x5, t), 0),
  Eq(Derivative(x6, t), 0),
  Eq(Derivative(x7, t), 0),
  Eq(Derivative(x8, t), 0),
  Eq(Derivative(x9, t), 0),
  Eq(Derivative(x10, t), 0),
  Eq(Derivative(x11, t), 0),
  Eq(Derivative(x12, t), 0),
  Eq(Derivative(x13, t), (1*(k1 + k2*k60 + k3*x13*x14 + k4*x13*x14*x15)/(1 + k5*k60 + k6*x13 + k7*x13*x14 + k8*x13*x14*x15 + k9*x17*x13 + k10*x18) + (-1)*k11*x13)/k50),
  Eq(Derivative(x14, t), (1*(k12 + k13*x13*x14 + k14*x13*x14*x15)/(1 + k15*x13 + k16*x13*x14 + k17*x13*x14*x15) + (-1)*k19*x14)/k50),
  Eq(Derivative(x15, t), (1*(k20 + k21*x13*x14 + k22*x13*x14*x15 + k23*k62)/(1 + k24*x13 + k25*x13*x14 + k26*x13*x14*x15 + k27*x13*x16 + k28*k62) + (-1)*k29*x15)/k50),
  Eq(Derivative(x16, t), (1*(k41 + k42*x13 + k43*x16)/(1 + k44*x13 + k45*x16 + k46*x15 + k47*k61) + (-1)*k48*x16)/k50),
  Eq(Derivative(x17, t), (1*(k30 + k31*x17)/(1 + k32*x17 + k33*x17*x13) + (-1)*k34*x17)/k50),
  Eq(Derivative(x18, t), (1*(k35 + k36*x17 + k37*x16)/(1 + k38*x17 + k39*x16) + (-1)*k40*x18)/k50),
  Eq(Derivative(x19, t), 0/k50),
  Eq(Derivative(x20, t), 0/k50) ]