We could basically take the interior stencils of `Mattsson2012`. See also - [Ramji Kamakoti and Carlos Pantano (2010) High-order narrow stencil finite-difference approximations of second-order derivatives involving variable coefficients](https://epubs.siam.org/doi/abs/10.1137/080740829)
We could basically take the interior stencils of
Mattsson2012. See also