Can you stump the Encyclopedia of Integer Sequences?

April 15, 2002 11:16 PM

Can you stump the Encyclopedia of Integer Sequences? Every identifiable sequence known to man, including:

Name: Busy Beaver problem: maximal number of steps that an n-state Turing machine can make on an initially blank tape before eventually halting.
Comment: The sequence grows faster than any computable function of n, and so is non-computable.
Keywords: hard,huge,nice,nonn,bref

If your sequence does not appear there, you might want to try the Super Seeker.
posted by vacapinta (9 comments total)

kinda impressive, i thought it'd be a piece of cake to spoof it with non-arithmetic sequences, but it has linguistic bases covered (the one i tried was numerical equivalence of first letter of month n, eg: n=1, jan=month1=10)
posted by juv3nal at 12:29 AM on April 16, 2002

Wow, it caught the pseudoprimes (although didn't bother to distinguish them from the Carmichael numbers.)

But I did stump it with 1, 11, 121, 111211, 311221,... I guess that's not serious mathematics.
posted by transona5 at 12:31 AM on April 16, 2002

1, 21, 25, 84, 95

i tried 3 more sequences none of which gave any results.
posted by Spoon at 1:21 AM on April 16, 2002

what's the pattern with the 1, 21, 25, 84, 95?
posted by juv3nal at 2:25 AM on April 16, 2002

Not serious? Heck, they've got the eban numbers.... 2,4,6,30,32,34,36,40,42... whose defining characteristic that there's no "e" in the spelling of these numbers.
posted by meep at 3:26 AM on April 16, 2002

there is no pattern to those particular numbers.

(please insert there is no spoon joke here)
posted by Spoon at 8:33 AM on April 16, 2002

transona5: what is that sequence? I'm familiar with a similar-looking (but different) sequence which the encyclopedia did know: 1, 11, 21, 1211, 111221, 312211, ....

Your sequence seems to follow the same rule, except for the third term, 121. How did you get that term?
posted by DevilsAdvocate at 9:26 AM on April 16, 2002

Try this one out:
4 14 23 34 42
posted by beagle at 10:01 AM on April 16, 2002

Oh. 21, of course. Oops.
posted by transona5 at 12:39 PM on April 16, 2002