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Six numbers and a prime (Posted on 2006-08-29) Difficulty: 2 of 5
Consider six consecutive positive integers. Show that there is a prime number that divides exactly one of them.

See The Solution Submitted by JLo    
Rating: 3.0000 (1 votes)

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Re Bertrand's postulate | Comment 20 of 23 |
(In reply to re: One conjecture dead, one still alive by JLo)

JLo:

Bertrand's postulate (which is proved) says that there is guaranteed to be a prime between n+1 and 2n, for any n > 2.  I don't believe that this helps prove that there is a prime number that divides exactly one of any n consecutive positive integers.  It only proves that, for n > 2, there is a prime number that divides exactly one of the n consectutive integers starting with n+1.  It doesn't, however, say anything about sequences of n integers whose first number is > n+1.

For instance, consider n = 10.
Bertrand's postulate guarantees that there is a prime number that divides exactly one of 11, 12, 13, ... 20.  It doesn't help at all if the sequence of 10 numbers starts with 12 or 13 or 1234789632.

  Posted by Steve Herman on 2006-09-09 20:20:27

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