English

The least common multiple of consecutive quadratic progression terms

Number Theory 2014-04-04 v2

Abstract

Let kk be an arbitrary given positive integer and let f(x)Z[x]f(x)\in {\mathbb Z}[x] be a quadratic polynomial with aa and DD as its leading coefficient and discriminant, respectively. Associated to the least common multiple lcm0ik{f(n+i)}{\rm lcm}_{0\le i\le k}\{f(n+i)\} of any k+1k+1 consecutive terms in the quadratic progression {f(n)}nN\{f(n)\}_{n\in \mathbb{N}^*}, we define the function gk,f(n):=(i=0kf(n+i))/lcm0ik{f(n+i)}g_{k, f}(n):=(\prod_{i=0}^{k}|f(n+i)|)/{\rm lcm}_{0\le i\le k}\{f(n+i)\} for all integers nNZk,fn\in \mathbb{N}^*\setminus Z_{k, f}, where Zk,f:=i=0k{nN:f(n+i)=0}Z_{k,f}:=\bigcup_{i=0}^k\{n\in \mathbb{N}^*: f(n+i)=0\}. In this paper, we first show that gk,fg_{k,f} is eventually periodic if and only if Da2i2D\ne a^2i^2 for all integers ii with 1ik1\le i\le k. Consequently, we develop a detailed pp-adic analysis of gk,fg_{k, f} and determine its smallest period. Finally, we obtain asymptotic formulas of loglcm0ik{f(n+i)}\log {\rm lcm}_{0\le i\le k}\{f(n+i)\} for all quadratic polynomials ff as nn goes to infinity.

Keywords

Cite

@article{arxiv.1208.5119,
  title  = {The least common multiple of consecutive quadratic progression terms},
  author = {Shaofang Hong and Guoyou Qian},
  journal= {arXiv preprint arXiv:1208.5119},
  year   = {2014}
}

Comments

32 pages. To appear in Forum Mathematicum