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 Unitary perfect numbers (Posted on 2013-12-16)
A unitary divisor of a number n is a number d such that d|n and gcd(d, n/d)=1. For example, 3 is a unitary divisor of 12 because gcd(3, 12/3)=gcd(3, 4)=1.

A unitary perfect number is a number that is the sum of its unitary divisors less than itself. For example, 60 is a unitary perfect number because its unitary divisors less than itself are 1, 3, 4, 5, 12, 15, and 20, and 1+3+4+5+12+15+20=60. Find all unitary perfect numbers less than 1000000.

 See The Solution Submitted by Math Man Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 re(4): just look up by SH Comment 10 of 10 |
(In reply to re(3): just look up by SH by Charlie)

I am with you regarding solution of crosswords, KENKEN , SUDOKO etc.

IMHO the subject puzzle does not  merit a D3 grading, which is misleading.
The value of it as a programming challenge appeals to very few of us, and since it is an open problem, - I see its value only as bringing to foreground a concept not widely known before.

 Posted by Ady TZIDON on 2013-12-17 10:16:06

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