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We describe a multiplicative normal form for rational functions which exhibits the shift structure of the factors, and investigate its properties. On the basis of this form we propose an algorithm which, given a rational function R, extracts a rational part F from the product of consecutive values of R: n−1 k=n 0 R(k) = F (n) n−1 k=n 0 V (k) where the… (More)

- S A Abramov, H Q Le, Z Li
- 2005

We present some algorithms related to rings of Ore polynomials (or, briefly, Ore rings) and describe a computer algebra library for basic operations in an arbitrary Ore ring. The library can be used as a basis for various algorithms in Ore rings, in particular, in differential, shift, and q-shift rings.

1 Introduction Let K be a field of characteristic O and L : K[Z]-+ K[Z] an endomorphism of the K-linear space of univariate poly-nomials over K. We consider the following computational tasks concerning L: Tl, T2< T3. Homogeneous equation Ly = O: Compute a basis of Ker L in K[z]. Inhomogeneous equation Ly = f: Given ~ 6 K[z], compute a basis of the affine… (More)

This paper is an exposition of different methods for computing closed forms of definite sums. The focus is on recently-developed results on computing closed forms of definite sums of hypergeometric terms. A design and an implementation of a software package which incorporates these methods into the computer algebra system Maple are described in detail.

A terminating condition of the well-known Zeilberger's algorithm for a given hypergeometric term <i>T</i>(<i>n, k</i>) is presented. It is shown that the only information on <i>T</i>(<i>n, k</i>) that one needs in order to determine in advance whether this algorithm will succeed is the rational function <i>T</i>(<i>n, k</i> + 1)/<i>T</i>(<i>n, k</i>).

Sufficient conditions are given for validity of the discrete Newton-Leibniz formula when the indefinite sum is obtained either by Gosper's algorithm or by Accurate Summation algorithm. It is shown that sometimes a polynomial can be factored from the summand in such a way that the safe summation range is increased.

We propose an algorithm to compute rational function solutions for a first order system of linear difference equations with rational coefficients. This algorithm does not require preliminary uncoupling of the given system.

We describe a new direct algorithm for transforming a linear system of recurrences into an equivalent one with nonsingular leading or trailing matrix. Our algorithm, which is an improvement to the EG elimination method [2], uses only elementary linear algebra operations (ranks, kernels and determinants) to produce an equation satisfied by the degrees of the… (More)

We present an algorithm which, given a hypergeometric term <i>T</i>(<i>n</i>), constructs hypergeometric terms <i>T</i><subscrpt>1</subscrpt>(<i>n</i>) and <i>T</i><subscrpt>2</subscrpt>(<i>n</i>) such that <i>T</i>(<i>n</i>) = <i>T</i><subscrpt>1</subscrpt>(<i>n</i> + 1) -<i>T</i><subscrpt>1</subscrpt>(<i>n</i>) + <i>T</i><subscrpt>2</subscrpt>(<i>n</i>),… (More)