From: renuka.medhavini on
Hi,

I am trying to solve for a system of 16 coupled differential equations
for a density matrix problem.

One of my initial conditions are that x13[t]+x14[t]+x15[t]+x16[t]==1 -
I do not know how to incorporate this in the system of equations as a
boundary condition. I get the error message

NDSolve::ndode: Input is not an ordinary differential equation.

Thanks, Medhavini