Efficiently compute central and off-diagonal blocks of the inverse of a block-tridiagonal matrix using O(N) recursive method of Rybicki & Hummer (1991).
Ref:
“An Accelerated Lambda Iteration Method for Multilevel Radiative Transfer” Rybicki, G.B., and Hummer, D.G., Astronomy and Astrophysics, 245, 171–181 (1991), Appendix B.