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On rough and smooth neighbors.

William D. Banks, Florian Luca, Igor E. Shparlinski (2007)

Revista Matemática Complutense

We study the behavior of the arithmetic functions defined byF(n) = P+(n) / P-(n+1) and G(n) = P+(n+1) / P-(n) (n ≥ 1)where P+(k) and P-(k) denote the largest and the smallest prime factors, respectively, of the positive integer k.

On Rowland's sequence.

Chamizo, Fernando, Raboso, Dulcinea, Ruiz-Cabello, Serafín (2011)

The Electronic Journal of Combinatorics [electronic only]

On ruled fields

Jack Ohm (1989)

Journal de théorie des nombres de Bordeaux

Some results and problems that arise in connection with the foundations of the theory of ruled and rational field extensions are discussed.

On s -fibonomials.

Pita Ruiz Velasco, Claudio de Jesús (2011)

Journal of Integer Sequences [electronic only]

On second 2-descent and non-congruent numbers

Yi Ouyang, Shenxing Zhang (2015)

Acta Arithmetica

We use the so-called second 2-descent method to find several series of non-congruent numbers. We consider three different 2-isogenies of the congruent elliptic curves and their duals, and find a necessary condition to estimate the size of the images of the 2-Selmer groups in the Selmer groups of the isogeny.

On self-similar subgroups in the sense of IFS

Mustafa Saltan (2018)

Communications in Mathematics

In this paper, we first give several properties with respect to subgroups of self-similar groups in the sense of iterated function system (IFS). We then prove that some subgroups of p -adic numbers p are strong self-similar in the sense of IFS.

On semiregular digraphs of the congruence x k y ( mod n )

Lawrence Somer, Michal Křížek (2007)

Commentationes Mathematicae Universitatis Carolinae

We assign to each pair of positive integers n and k 2 a digraph G ( n , k ) whose set of vertices is H = { 0 , 1 , , n - 1 } and for which there is a directed edge from a H to b H if a k b ( mod n ) . The digraph G ( n , k ) is semiregular if there exists a positive integer d such that each vertex of the digraph has indegree d or 0. Generalizing earlier results of the authors for the case in which k = 2 , we characterize all semiregular digraphs G ( n , k ) when k 2 is arbitrary.

On sequences over a finite abelian group with zero-sum subsequences of forbidden lengths

Weidong Gao, Yuanlin Li, Pingping Zhao, Jujuan Zhuang (2016)

Colloquium Mathematicae

Let G be an additive finite abelian group. For every positive integer ℓ, let d i s c ( G ) be the smallest positive integer t such that each sequence S over G of length |S| ≥ t has a nonempty zero-sum subsequence of length not equal to ℓ. In this paper, we determine d i s c ( G ) for certain finite groups, including cyclic groups, the groups G = C C 2 m and elementary abelian 2-groups. Following Girard, we define disc(G) as the smallest positive integer t such that every sequence S over G with |S| ≥ t has nonempty zero-sum subsequences...

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