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Lucky Numbers (Posted on 2005-02-19) Difficulty: 4 of 5
Call an integer lucky if it is a sum of positive integers (not necessarily distinct) whose reciprocals sum to 1. For example, 4 and 11 are lucky: 4=2+2 and 1/2+1/2=1, and 11=2+3+6 and 1/2+1/3+1/6=1. But 2, 3, and 5 are unlucky. How many unlucky positive integers are there?

See The Solution Submitted by David Shin    
Rating: 3.7500 (4 votes)

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  Subject Author Date
SolutionUnlucky numberMath Man2011-04-09 16:54:46
AnswerK Sengupta2008-03-21 14:58:52
solutionparvez2005-02-21 13:31:12
IdeasGamer2005-02-21 02:53:01
SolutionBelieve it or not!Old Original Oskar!2005-02-19 16:30:48
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