Primitive abundant and weird numbers with many prime factors
Abstract
We give an algorithm to enumerate all primitive abundant numbers (briefly, PANs) with a fixed (the number of prime factors counted with their multiplicity), and explicitly find all PANs up to , count all PANs and square-free PANs up to and count all odd PANs and odd square-free PANs up to . We find primitive weird numbers (briefly, PWNs) with up to 16 prime factors, improving the previous results of [Amato-Hasler-Melfi-Parton] where PWNs with up to 6 prime factors have been given. The largest PWN we find has 14712 digits: as far as we know, this is the largest example existing, the previous one being 5328 digits long [Melfi]. We find hundreds of PWNs with exactly one square odd prime factor: as far as we know, only five were known before. We find all PWNs with at least one odd prime factor with multiplicity greater than one and and prove that there are none with . Regarding PWNs with a cubic (or higher) odd prime factor, we prove that there are none with , and we did not find any with larger . Finally, we find several PWNs with 2 square odd prime factors, and one with 3 square odd prime factors. These are the first such examples.
Keywords
Cite
@article{arxiv.1802.07178,
title = {Primitive abundant and weird numbers with many prime factors},
author = {Gianluca Amato and Maximilian F. Hasler and Giuseppe Melfi and Maurizio Parton},
journal= {arXiv preprint arXiv:1802.07178},
year = {2019}
}
Comments
New section on open problems. A mistake in table 2 corrected (# odd PAN with Omega=8). New PWN in table 5, last line, 2 squared prime factors, Omega=15. Updated bibliography