[seqfan] Re: A220952 "unkn" (author Don Knuth, Feb 20, 2013) - continuation?

Neil Sloane njasloane at gmail.com
Fri Aug 25 16:06:37 CEST 2017

I did some editing of the Knuth sequence A220952.  But the essential
thing is still missing, namely, how is the sequence defined?

The first link will show you the statement of the problem, without you
having to pay. But it is hard to follow.

The second link is useless, unless you have access to JSTOR, it is
basically an ad, an invitation for you to spend $19.00.

I have the issue of the Monthly with the problem and solution and
could send a copy to anyone who wants to help.

I'm confused by one point: the problem says each positive integer is
adjacent to exactly two positive integers. But 1, 2, 3, and 4 are all
mutually adjacent (since the condition is vacuous for single-digit
numbers), so 1 is adjacent to three numbers, 2, 3, and 4.

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