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Matching pairs (Posted on 2015-07-24) Difficulty: 3 of 5
(7,13); (73,137); (41,271);

Both members of each of the above sets share a certain unique feature.

What feature ?

See The Solution Submitted by Ady TZIDON    
Rating: 5.0000 (1 votes)

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Solution Solution Comment 1 of 1
They are the primes p such that 1/p has a certain period.

1/7=0.142857142857...
1/13=0.076923076923...
period=6

1/73=0.0136986301369863...
1/137=0.0072992700729927...
period=8

1/41=0.0243902439...
1/271=0.0036900369...
period=5


  Posted by Math Man on 2015-07-24 14:32:07
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