[seqfan] Re: easy and bref

franktaw at netscape.net franktaw at netscape.net
Fri Sep 30 19:39:12 CEST 2011

Thanks, that's an example of what Charles was looking for. The busy 
beaver problem is provably hard - we know that we won't be able to find 
a formula for it.

Franklin T. Adams-Watters

-----Original Message-----
From: D. S. McNeil <dsm054 at gmail.com>

I guess I don't see "hard" as a permanent property but as a
description of our state of knowledge.  Right now, A060843 -- the busy
beaver problem -- only has four known terms, and not for lack of
interest.  Why only four?  Because the sequence is hard in the
colloquial sense.  If someone comes up with a formula and we suddenly
had lots of terms, we'd simply remove "hard", like we remove "obsc"
after someone cleans up a sequence in bad shape.

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