  Exact solvability of the discretized N-point version of the PT-symmetric
square-well model is pointed out. Its wave functions are found proportional to
the classical Tshebyshev polynomials of a complex argument. At all N a compact
secular equation is derived giving the real spectrum of energies at any
non-Hermiticity strength Z below its finite and weakly N-dependent critical
value. In the limit of vanishing Z the model degenerates to a Hermitian Hueckel
Hamiltonian.
