English

A variation of a congruence of Subbarao for n=2^(alpha)*5^(beta)

Number Theory 2016-07-06 v1

Abstract

There are many open problems concerning the characterization of the positive integers nn fulfilling certain congruences and involving the Euler totient function φ\varphi and the sum of positive divisors function σ\sigma of the positive integer nn. In this work, we deal with the congruence of the form nφ(n)2(modσ(n)) n\varphi(n)\equiv2\pmod{\sigma(n)} and we prove that the only positive integers of the form 2α5β,α,β0,2^{\alpha}5^{\beta}, \enspace \alpha, \beta\geq0, that satisfy the above congruence are n=1,2,5,8n=1, 2, 5, 8.

Keywords

Cite

@article{arxiv.1607.01258,
  title  = {A variation of a congruence of Subbarao for n=2^(alpha)*5^(beta)},
  author = {Sanda Bujačić},
  journal= {arXiv preprint arXiv:1607.01258},
  year   = {2016}
}