English

Practical central binomial coefficients

Number Theory 2020-04-14 v1

Abstract

A practical number is a positive integer nn such that all positive integers less than nn can be written as a sum of distinct divisors of nn. Leonetti and Sanna proved that, as x+x \to +\infty, the central binomial coefficient (2nn)\binom{2n}{n} is a practical number for all positive integers nxn \leq x but at most O(x0.88097)O(x^{0.88097}) exceptions. We improve this result by reducing the number of exceptions to exp ⁣(C(logx)4/5loglogx)\exp\!\big(C (\log x)^{4/5} \log \log x\big), where C>0C > 0 is a constant.

Keywords

Cite

@article{arxiv.2004.05376,
  title  = {Practical central binomial coefficients},
  author = {Carlo Sanna},
  journal= {arXiv preprint arXiv:2004.05376},
  year   = {2020}
}