Journal of Integer Sequences, Vol. 28 (2025), Article 25.5.3

On Modular Representations of C-Recursive Integer Sequences


M. Prunescu
University of Bucharest
Research Center for Logic, Optimization and Security (LOS)
Faculty of Mathematics and Computer Science
Academiei 14
Bucharest (RO-010014)
Romania
and
Institute of Logic and Data Science
Bucharest
Romania
and
Simion Stoilow Institute of Mathematics of the Romanian Academy
Research Unit 5
P. O. Box 1-764
Bucharest (RO-014700)
Romania

J. M. Shunia
Independent Researcher
Ann Arbor, MI
USA

Abstract:

Prunescu and Sauras-Altuzarra showed that all C-recursive sequences of natural numbers have an arithmetic div-mod representation that can be derived from their generating function. This representation consists of computing the quotient of two exponential polynomials and taking the remainder of the result modulo a third exponential polynomial, and works for all integers n ≥ 1. Using a different approach, Prunescu proved the existence of two other representations, one of which is the mod-mod representation, consisting of two successive remainder computations. This result has two weaknesses: the representation works only ultimately, and a correction term must be added to the first exponential polynomial. We show that a mod-mod representation without inner correction term holds for all integers n ≥ 1. This follows directly from the div-mod representation by an arithmetic short-cut from outside.


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(Concerned with sequences A000032 A000045 A000051 A000073 A000129 A000225 A000930 A000931 A001080 A001081 A001477 A002203 A002249 A007395 A088137.)


Received March 11 2025; revised versions received March 12 2025; September 16 2025. Published in Journal of Integer Sequences, September 16 2025.


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