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MathGroup Archive 1999

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Re: Numbers problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19533] Re: [mg19520] Numbers problem
  • From: Hans Havermann <haver at total.net>
  • Date: Tue, 31 Aug 1999 00:52:23 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

It's called "Langford's Problem". It first appeared around 1958 and was
popularized by Martin Gardner ten years later.

Here are the number of *pairs* of solutions:

 3:               1
 4:               1

 7:              26
 8:             150

11:          17,792
12:         108,144

15:      39,809,640
16:     326,721,800

19: 256,814,891,280
20:               ?

The case for n = 19 was just solved a few months ago: It took 4 people two
months of computing!

See: http://www.lclark.edu/~miller/langford.html




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