Principal Functions of Non-Selfadjoint Difference Operator with Spectral Parameter in Boundary Conditions

We investigate the principal functions corresponding to the eigenvalues and the spectral singularities of the boundary value problem (BVP) a(n-1)y(n-1) + b(n)y(n) + a(n)y(n+1) = lambda y(n), n is an element of N and (gamma(0) + gamma(1)lambda)y(1) + (beta(0) + beta(1)lambda)y(0) = 0, where (a(n)) and (b(n)) are complex sequences,. is an eigenparameter, and gamma(i), beta(i) is an element of C for i = 0, 1.