  We present a further development of methods for analytical calculations of
Green's functions of lattice fermions based on recurrence relations. Applying
it to tight-binding systems and topological superconductors in different
dimensions we obtain a number of new results. In particular we derive an
explicit expression for arbitrary Green's function of an open Kitaev chain and
discover non-local fermionic corner states in a 2D p-wave superconductor.
