English

Solutions of the problem of Erd\"os-Sierpi\'nski: $\sigma(n)=\sigma(n+1)$

Number Theory 2007-07-17 v1

Abstract

For n1.51010n\leq 1.5 \cdot 10^{10}, we have found a total number of 1268 solutions to the Erd\"os-Sierpi\'nski problem finding positive integer solutions of σ(n)=σ(n+1)\sigma(n)=\sigma(n+1), where σ(n)\sigma(n) is the sum of the positive divisors of n. On the basis of that set of solutions the following empirical properties are enunciated: first, all the σ(n)\sigma(n), nn being a solution, are divisible by 6; second, the repetition of solutions leads to the formulation of a new problem: \emph{Find the natural numbers nn such that σ(n)=σ(n+1)=σ(n+k)=σ(n+k+1)\sigma(n)=\sigma(n+1)=\sigma(n+k)=\sigma(n+k+1) for some positive integer kk}. A third empirical property concerns the asymptotic behavior of the function of nn that gives the number of solutions for mm less or equal to nn, which we find to be as n1/3n^{1/3}. Finally some theorems related to the Erd\"os-Sierpi\'nski problem are enunciated and proved.

Keywords

Cite

@article{arxiv.0707.2190,
  title  = {Solutions of the problem of Erd\"os-Sierpi\'nski: $\sigma(n)=\sigma(n+1)$},
  author = {Lourdes Benito},
  journal= {arXiv preprint arXiv:0707.2190},
  year   = {2007}
}