No subject

N. J. A. Sloane njas at
Fri Aug 31 18:34:59 CEST 2001

 From felice.russo at  Fri Aug 31 11:35:17 2001
Return-Path: <felice.russo at>
From: felice.russo at
Delivered-To: njas at
To: njas at
Subject: unitary untouchable numbers
Date: Fri, 31 Aug 2001 17:35:09 +0200
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Message-Id: <20010831153218.OKON19174.mta3@[]>
Status: R

I would like to extend the concept of untouchable numbers to the unitary divisors. So the definiton of unitary untouchable numbers should be:

The numbers n such that us(x)=n has no solution where us(x) is the sum of unitary proper divisors of x.

With a ubasic code for n<=10^5 I have found the following ones:

2 3 4 5 7 374 702 758 926 930 998

But how I can sure that none of those became solution of us(x)=n for larger values of n (>10^5)?

Is there any theoretical approach to prove that a number is unitary untouchable?

Thanks.  Felice


More information about the SeqFan mailing list