**Volume 16** ▶ Number 1 ▷ Number 2 ▷ Number 3 ▷ Number 4

**An improved solution of Σ _{i=1}^{k} 1/X_{i} = 1 in distinct integers when x_{i} ∤ x_{j} for i ≠ j**

*Original research paper. Pages 1–4*

Nechemia Burshtein

Full paper (PDF, 130 Kb) | Abstract

*k*= 52,

*x*

_{52}= 1963 is exhibited. This is the best known result thus far.

**On the solvability of homogeneous two-sided systems in max-algebra**

*Original research paper. Pages 5–15*

A. Aminu

Full paper (PDF, 247 Kb) | Abstract

*a*⊕

*b*= max(

*a*,

*b*) and

*a*⊗

*b*=

*a+b*for

*a*,

*b*∈ ℝ and extend the pair of operations to matrices and vectors in the same way as in linear algebra. The homogeneous twosided system in max-algebra is of the form

*A*⊗

*x*=

*B*⊗

*x*. No polynomial method for solving homogeneous system is known. In this paper, we consider homogeneous twosided linear systems in max-algebra in a special case. We show that it can be checked in O(

*n*

^{3}) time whether a given two-sided homogeneous system belongs to this special case. Solvability can be decided in O(

*n*

^{3}) time and in the positive case a solution can be found in O(

*n*

^{3}).

**Infinitely many insolvable Diophantine equations. II**

*Original research paper. Pages 16–23*

Yasutsugu Fujita and Noriaki Kimura

Full paper (PDF, 196 Kb) | Abstract

*f*(

*X*

_{1}, …,

*X*) be a quadratic form in m variables

_{m}*X*

_{1}, …,

*X*with integer coefficients. Then it is well-known that the Diophantine equation

_{m}*f*(

*X*

_{1}, …,

*X*) = 0 has a nontrivial solution in integers if and only if the equation has a nontrivial solution in real numbers and the congruence

_{m}*f*(

*X*

_{1}, …,

*X*) ≡ 0 (mod

_{m}*N*) has a nontrivial solution for every integer

*N*> 1. Such a principle is called the Hasse principle. In this paper, we explicitly give several types of families of the Diophantine equations of degree two, not homogeneous, for which the Hasse principle fails.

**Combined 2-Fibonacci sequences**

*Original research paper. Pages 24–28*

Krassimir Atanassov

Full paper (PDF, 123 Kb)

**Rows of odd powers in the modular ring Z _{4}**

*Original research paper. Pages 29–32*

J. V. Leyendekkers, A. Shannon

Full paper (PDF, 41 Kb) | Abstract

_{4}, wherein integer

*N*is represented by

*N*= 4

*r*+

_{i}*i*,

*i*= 0, 1, 2, 3. These row functions are based on the row functions for squares. When 3 ∤ N , the row of

*N*

^{2}= 3

*n*(3

*n*±1) , or when 3|

*N*, the row of

*N*

^{2}= 2 + 18(½

*n*(

*n*+1)),

*n*= 0, 1, 2, 3…

**A note on some diagonal, row and partial column sums of a Zeckendorf triangle**

*Original research paper. Pages 33–36*

A. G. Shannon

Full paper (PDF, 114 Kb) | Abstract