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0, 1, 2, 720!

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Patrick Crotty

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Apr 18, 1995, 3:00:00 AM4/18/95
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Some said that this is the sequence
1!!!, 2!!!, 3!!!, and that the next entry would be 4!!!. But
what about 0? I've always seen 0! defined as 1, not 0, and so
unless I'm completely missing something, the original puzzle
should have been called 1, 1, 2, 720!. It seems to me that
a more correct solution, if 0 is to be included, would be
0, 1!, 2!!, 3!!!, and so the next entry would be 4!!!!, not 4!!!.
Agai, though, I'm not sure about this, so please tell me if
I'm wrong.

Patrick Crotty
p...@physics.wm.edu


Jan Ritsema van Eck

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Apr 20, 1995, 3:00:00 AM4/20/95
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In article <1995Apr18....@cs.wm.edu> p...@physics.wm.edu (Patrick Crotty) writes:
>From: p...@physics.wm.edu (Patrick Crotty)
>Subject: Re: 0, 1, 2, 720!
>Date: Tue, 18 Apr 1995 23:30:52 GMT

>Some said that this is the sequence
>1!!!, 2!!!, 3!!!, and that the next entry would be 4!!!. But

Make that 1!!, 2!!, 3!! (3! = 6, 6! = 720; of course for 1 and 2 the number
of !'s doesn't make any difference)

>what about 0? I've always seen 0! defined as 1, not 0, and so

That's what bothered me, too

>unless I'm completely missing something, the original puzzle
>should have been called 1, 1, 2, 720!. It seems to me that
>a more correct solution, if 0 is to be included, would be
>0, 1!, 2!!, 3!!!, and so the next entry would be 4!!!!, not 4!!!.

No. See above, 3!!! = 720! (a number I am not going to compute).
^this is a mathematical '!', not a punctuation mark

Still puzzled. What did we miss?

Seth Breidbart

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Apr 20, 1995, 3:00:00 AM4/20/95
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In article <j.ritsema....@frw.ruu.nl>,

Jan Ritsema van Eck <j.ri...@frw.ruu.nl> wrote:
>In article <1995Apr18....@cs.wm.edu> p...@physics.wm.edu (Patrick Crotty) writes:
>>From: p...@physics.wm.edu (Patrick Crotty)

>>Some said that this is the sequence


>>1!!!, 2!!!, 3!!!, and that the next entry would be 4!!!. But
>Make that 1!!, 2!!, 3!! (3! = 6, 6! = 720; of course for 1 and 2 the number
>of !'s doesn't make any difference)

No, you _want_ 720!.

>>what about 0? I've always seen 0! defined as 1, not 0, and so
>That's what bothered me, too
>>unless I'm completely missing something, the original puzzle
>>should have been called 1, 1, 2, 720!. It seems to me that
>>a more correct solution, if 0 is to be included, would be
>>0, 1!, 2!!, 3!!!, and so the next entry would be 4!!!!, not 4!!!.
>No. See above, 3!!! = 720! (a number I am not going to compute).
> ^this is a mathematical '!', not a punctuation mark
>Still puzzled. What did we miss?

The last character in the Subject: header?

Seth


David Karr

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Apr 20, 1995, 3:00:00 AM4/20/95
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In article <j.ritsema....@frw.ruu.nl> j.ri...@frw.ruu.nl (Jan Ritsema van Eck) writes:
>In article <1995Apr18....@cs.wm.edu> p...@physics.wm.edu (Patrick Crotty) writes:
>>From: p...@physics.wm.edu (Patrick Crotty)
>>Subject: Re: 0, 1, 2, 720!
^^^^
>Make that 1!!, 2!!, 3!! [...]

>
>>a more correct solution, if 0 is to be included, would be
>>0, 1!, 2!!, 3!!!, and so the next entry would be 4!!!!, not 4!!!.
>
>No. See above, 3!!! = 720! (a number I am not going to compute).

See above indeed. I see 720! following 2 in the sequence. I do not
see 3!! = 720 in the sequence.

In any case, 0!! = 1, so where did the initial 0 come from? It's the
initial 0 that causes people to guess 0, 1!, 2!!, 3!!!, 4!!!! rather
than any of the sequences with a constant number of apllications of
factorial.

-- David A. Karr (ka...@cs.cornell.edu)


Dave Ring

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Apr 20, 1995, 3:00:00 AM4/20/95
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David Karr <ka...@cs.cornell.edu> wrote:
>>>Subject: Re: 0, 1, 2, 720!
>In any case, 0!! = 1, so where did the initial 0 come from? It's the
>initial 0 that causes people to guess 0, 1!, 2!!, 3!!!, 4!!!! rather
>than any of the sequences with a constant number of apllications of
>factorial.

Another reasonable possibility for the next number is (720!+1)!!!
--
Dave Ring
dwr...@tam2000.tamu.edu


Philip Gibbs

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Apr 21, 1995, 3:00:00 AM4/21/95
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In article <3n64t5$l...@glitnir.cs.cornell.edu>, ka...@cs.cornell.edu (David Karr) writes:
>>
> In any case, 0!! = 1, so where did the initial 0 come from? It's the
> initial 0 that causes people to guess 0, 1!, 2!!, 3!!!, 4!!!! rather
> than any of the sequences with a constant number of apllications of
> factorial.
>

or perhaps its generated recursively from

x -> (x+1)!!

or, depending on how you interpret the ! in the sequence

x -> (x+1)!!!

so the next number is 721!! or (720!+1)!!!


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