There are many examples of potentials $V(x)$ for which Schrodinger's equation for a single particle in one dimension is exactly solvable, in the sense that we can give "nice" expressions for the eigenfunctions and eigenvalues of the operator $-\frac{1}{2}\partial_x^2+V(x)$; I do not know if there is a technical definition of "nice" here, but standard examples include the harmonic oscillator $V(x)=\frac{1}{2}x^2$, as well as the hydrogen atom, $V(x)=-1/x$. In some cases, there are also similarly nice expressions for time evolution under this operator.
Suppose we instead consider the operator $\partial_x D(x) \partial_x$, either on $\mathbb{R}$ or on an interval with some given boundary conditions. Are there known examples of functions $D(x)$, other than the trivial constant example, for which there are similarly nice expressions?