{ diff(x1, t) = ((-1)*k2*(k3*x1*x3 - k4*x13) + 1*k2*k5*x13)/k2,
  diff(x2, t) = ((-1)*k2*(k6*x2*x4 - k7*x14) + 1*k2*k8*x14)/k2,
  diff(x3, t) = ((-1)*k2*(k3*x1*x3 - k4*x13) + 1*k2*k8*x14)/k2,
  diff(x4, t) = (1*k2*k5*x13 + (-1)*k2*(k6*x2*x4 - k7*x14) + (-1)*k2*(k9*x5*x4 - k10*x15) + 1*k2*k11*x15 + (-1)*k2*(k15*x6*x4 - k16*x16) + 1*k2*k17*x16)/k2,
  diff(x5, t) = ((-1)*k2*(k9*x5*x4 - k10*x15) + 1*k2*k14*x20)/k2,
  diff(x6, t) = (1*k2*k11*x15 + (-1)*k2*(k12*x6*x12 - k13*x20) + (-1)*k2*(k15*x6*x4 - k16*x16) + 1*k2*k20*x19)/k2,
  diff(x7, t) = (1*k2*k17*x16 + (-1)*k2*(k18*x7*x12 - k19*x19) + (-1)*k2*(k21*x8*x7 - k22*x17) + 1*k2*k23*x17 + (-1)*k2*(k27*x9*x7 - k28*x18) + 1*k2*k29*x18)/k2,
  diff(x8, t) = ((-1)*k2*(k21*x8*x7 - k22*x17) + 1*k2*k26*x22)/k2,
  diff(x9, t) = (1*k2*k23*x17 + (-1)*k2*(k24*x9*x11 - k25*x22) + (-1)*k2*(k27*x9*x7 - k28*x18) + 1*k2*k32*x21)/k2,
  diff(x10, t) = (1*k2*k29*x18 + (-1)*k2*(k30*x10*x11 - k31*x21))/k2,
  diff(x11, t) = ((-1)*k2*(k24*x9*x11 - k25*x22) + 1*k2*k26*x22 + (-1)*k2*(k30*x10*x11 - k31*x21) + 1*k2*k32*x21)/k2,
  diff(x12, t) = ((-1)*k2*(k12*x6*x12 - k13*x20) + 1*k2*k14*x20 + (-1)*k2*(k18*x7*x12 - k19*x19) + 1*k2*k20*x19)/k2,
  diff(x13, t) = (1*k2*(k3*x1*x3 - k4*x13) + (-1)*k2*k5*x13)/k2,
  diff(x14, t) = (1*k2*(k6*x2*x4 - k7*x14) + (-1)*k2*k8*x14)/k2,
  diff(x15, t) = (1*k2*(k9*x5*x4 - k10*x15) + (-1)*k2*k11*x15)/k2,
  diff(x16, t) = (1*k2*(k15*x6*x4 - k16*x16) + (-1)*k2*k17*x16)/k2,
  diff(x17, t) = (1*k2*(k21*x8*x7 - k22*x17) + (-1)*k2*k23*x17)/k2,
  diff(x18, t) = (1*k2*(k27*x9*x7 - k28*x18) + (-1)*k2*k29*x18)/k2,
  diff(x19, t) = (1*k2*(k18*x7*x12 - k19*x19) + (-1)*k2*k20*x19)/k2,
  diff(x20, t) = (1*k2*(k12*x6*x12 - k13*x20) + (-1)*k2*k14*x20)/k2,
  diff(x21, t) = (1*k2*(k30*x10*x11 - k31*x21) + (-1)*k2*k32*x21)/k2,
  diff(x22, t) = (1*k2*(k24*x9*x11 - k25*x22) + (-1)*k2*k26*x22)/k2 }