 
Summary: Continuation of Holomorphic Solutions of Linear Di#erence
Equations with Polynomial Coe#cients
S. A. Abramov and M. A. Barkatou
Computing Center of RAS, Limoges University
We consider a linear di#erence operator
L = a d (z)E d + ˇ ˇ ˇ + a 1 (z)E + a 0 (z), (1)
and the corresponding linear di#erence equation Ly = 0. Here the coe#cients
a i (z) are polynomial over C and E is the ``shift operator'' acting on functions
of the complex variable z as Ey(z) = y(z + 1). The di#erence operator L is an
element of the noncommutative ring C[z, E]. We shall call a d the leading coef
ficient and a 0 the trailing coe#cient of L and we shall suppose that a 0 a d #= 0.
We shall call the singularities of both L and Ly = 0 the zeros of the polyno
mials a 0 (z) and a d (z  d). A point p # C will be said to be congruent to the
singularities of L if a 0 (p +#) = 0 or a d (p #) = 0 for some nonnegative integer
#.
Equation Ly = 0 can be used as a tool to define a sequence or a function. If
we know the value y(z) at every point z of a given strip # # Re z < # + d we
can find the value of y(z) in the strip #  1 # Re z < # , and hence in the strip
#  2 # Re z < #  1, and so on. We can continue y(z) indefinitely to the left
except at the points that are congruent to the zeros of the trailing coe#cient
