Derived from Koslov, Evasiveness Conjecture; Fwd: SEQ FROM Jonathan Vos Post

N. J. A. Sloane njas at research.att.com
Mon Mar 3 13:44:30 CET 2008


so I rejected it!
 %N A000001 The number of vertices for which the Evasiveness
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From: "N. J. A. Sloane" <njas at research.att.com>
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Subject: Re: emirp formed by concatenating primitive Pythagorean triples
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Me: you are correct!
 Best regards
 			 Neil
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From: "N. J. A. Sloane" <njas at research.att.com>
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To: jvospost3 at gmail.com, maxale at gmail.com
Subject: Re: Derived from Koslov, Evasiveness Conjecture; Fwd: SEQ FROM Jonathan Vos Post
Cc: seqfan at ext.jussieu.fr
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 Best regards
 			 Neil
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From: hv at crypt.org
Subject: square-free ternary numbers
Date: Mon, 03 Mar 2008 17:03:48 +0000
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squarefree string, it is "critical", in the sense that disallowing any
  3, 8, 9, 18, 20, 20, 21, 38, 39, 42, 42, 42, 44, 44, 45, 78, 79, 80, 81, 86,
  86, 86, 86, 86, 87, 90, 90, 90, 92, 92, 93, 158
  n=40 => 174; n=80 => 350.
  6, 38, 55, 224, 292, 335, 378, 1216, 1320, 1601, 1703, 1805, 2009, 2110,
  2210, 6374, 6613, 6851, 7085, 8275, 8508, 8741, 8974, 9207
  n=40 => 41499; n=80 => 206743.
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Subject: Re: square-free ternary numbers
From: "Russ Cox" <rsc at swtch.com>
Date: Mon, 3 Mar 2008 17:37:16 -0500
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> Of particular interest is the pair (010, 212). I cannot be certain that
> this yields an infinite string, since I am relying only on observation of

You might be interested in 

Narad Rampersad, ``A note on avoidable words in ternary strings''
http://arxiv.org/abs/math/0307363v1

The fact that you can build an infinite square-free
string without 010 and 212 follows from the construction
used in Theorem 2.  (The construction actually avoids 101 and 202.)

> Alternatively expressed: it appears that any infinite squarefree string that
> avoids the substrings 010 and 212 must necessarily contain every other
> allowable substring, of any length.

The paper has nothing to say about this question, though.

Russ






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