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# Can you stump the Encyclopedia of Integer Sequences?

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# Can you stump the Encyclopedia of Integer Sequences?

April 15, 2002 11:16 PM Subscribe

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

If your sequence does not appear there, you might want to try the Super Seeker.

*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,brefComment: 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.

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

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

i tried 3 more sequences none of which gave any results.

posted by Spoon at 1:21 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

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

(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

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

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posted by juv3nal at 12:29 AM on April 16, 2002