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From: brianc@cognos.uucp (Brian Campbell)
Newsgroups: comp.lang.pascal
Subject: Re: Perfect number program
Message-ID: <1557@cognos.UUCP>
Date: Mon, 12-Oct-87 22:36:13 EDT
Article-I.D.: cognos.1557
Posted: Mon Oct 12 22:36:13 1987
Date-Received: Thu, 15-Oct-87 06:48:16 EDT
References: <9652@brl-adm.ARPA>
Reply-To: brianc@cognos.UUCP (Brian Campbell)
Organization: Cognos Incorporated, Ottawa, Canada
Lines: 23

In article <9652@brl-adm.ARPA> 11SSTEIN%GALLUA.BITNET@wiscvm.wisc.EDU writes:
! 
!  I am working on a perfect number program and I have faced some problems.
! 
!  Notice: A perfect number is a number that has its divisors add up to itself.
!  I.E. 6 = 1 + 2 + 3 = 6
!      28 = 1 + 2 + 4 + 7 + 14 = 28
! 
!      All that... you have an idea on a good program?

   I'm not sure whether your program is supposed to generate ALL perfect
numbers or not.  Nor am I sure the following produces all of the perfect
numbers.  Anyway, I remember some math text that listed the theory (?) that
if:

   (2 ^ n) - 1   is prime, then
   [(2 ^ n) - 1] * (2 ^ [n - 1])   is perfect

   Hope this helps...
-- 
Brian Campbell        uucp: decvax!utzoo!dciem!nrcaer!cognos!brianc
Cognos Incorporated   mail: POB 9707, 3755 Riverside Drive, Ottawa, K1G 3Z4
(613) 738-1440        fido: sysop@163/8