Let $G$ be an abelian group and $A,B$ two subsets of equal size $k$ such that $A+B$ and $A+A$ both have size $2k-1$. Answering a question of Bihani and Jin, we prove that if $A+B$ is aperiodic or if there exist elements $a\in A$ and $b\in B$ such that $a+b$ has a unique expression as an element of $A+B$ and $a+a$ has a unique expression as an element of $A+A$, then $A$ is a translate of $B$. We also give an explicit description of the various counterexamples which arise when neither condition holds.

Consider the system $x^2-a{y}^2=b$, $P(x,y)=z^2$, where $P$ is a given integer polynomial. Historically, the integer solutions of such systems have been investigated by many authors using the congruence arguments and the quadratic reciprocity. In this paper, we use Kedlaya’s procedure and the techniques of using congruence arguments with the quadratic reciprocity to investigate the solutions of the Diophantine equation $7X^2+Y^7=Z^2$ if $(X,Y)=(L_n,F_n)$ (or $(X,Y)=(F_n,L_n)$) where $\left\{F_n\right\}$ and $\left\{L_n\right\}$ represent the sequences of Fibonacci numbers and Lucas numbers respectively....

We obtain solutions to some conjectures about the nonlinear difference equation $$x_{n+1}=\alpha +\beta x_{n-1}{\mathrm{e}}^{-x_n},n=0,1,\cdots ,\alpha ,\beta >0.$$ More precisely, we get not only a condition under which the equilibrium point of the above equation is globally asymptotically stable but also a condition under which the above equation has a unique positive cycle of prime period two. We also prove some further results.

We show that if A and B are finite sets of real numbers, then the number of triples (a,b,c) ∈ A × B × (A ∪ B) with a + b = 2c is at most (0.15+o(1))(|A|+|B|)² as |A| + |B| → ∞. As a corollary, if A is antisymmetric (that is, A ∩ (-A) = ∅), then there are at most (0.3+o(1))|A|² triples (a,b,c) with a,b,c ∈ A and a - b = 2c. In the general case where A is not necessarily antisymmetric, we show that the number of triples (a,b,c) with a,b,c ∈ A and a - b = 2c is at most (0.5+o(1))|A|². These estimates...

Let $G$ be a group and let $X$ be a finite subset. The isoperimetric method investigates the objective function $\left|\right(XB)\setminus X|$, defined on the subsets $X$ with $\left|X\right|\ge k$ and $|G\setminus (XB\left)\right|\ge k$, where $XB$ is the product of $X$ by $B$.In this paper we present all the basic facts about the isoperimetric method. We improve some of our previous results and obtain generalizations and short proofs for several known results. We also give some new applications.Some of the results obtained here will be used in coming papers to improve Kempermann structure...

We consider alternating sums of squares of odd and even terms of the Lucas sequence and alternating sums of their products. These alternating sums have nice representations as products of appropriate Fibonacci and Lucas numbers.

This paper is a continuation of a recent paper [2], in which the authors studied some Markov matrices arising from a mapping T:ℤ → ℤ, which generalizes the famous 3x+1 mapping of Collatz. We extended T to a mapping of the polyadic numbers $\widehat{\mathbb{Z}}$ and construct finitely many ergodic Borel measures on $\widehat{\mathbb{Z}}$ which heuristically explain the limiting frequencies in congruence classes, observed for integer trajectories.