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Re: prime numbers and African artifact
Dave Oldridge (doldridg@fox.nstn.ns.ca)
10 Jul 1995 17:31:41 -0300
In article <3tp5m0$u27@news.sas.ab.ca>,
davidwss@freenet.edmonton.ab.ca () wrote:
> Rob Freundlich (rsf@mother.idx.com) wrote:
> : In article <5JUL199517392971@almach.caltech.edu>,
> : shoppa@almach.caltech.edu (Timothy D. Shoppa) wrote:
> : >In article <DB8qqE.3uI@undergrad.math.uwaterloo.ca>,
> : shallit@graceland.uwaterloo.ca (Jeffrey Shallit) writes...
> : >> "A piece of bone found in Africa and dated at around 8,500 B.C.
> : >>has engraved markings containing what appear to be representations of
> : >>the numbers 11, 13, 17, and 19, all of which are prime numbers ..."
> : >>
> : >What? They left out 9, 15, and 21, some of the most useful prime numbers
> : >of all! :^)
>
> : No, no, no. Those are the *even* numbers! The primes are 1, 4, 9, 16, 25,
> : 36, etc.
>
> Wrong - those are ROUND numbers. The primes are 1, 1, 2, 3, 5, 8, 13,
> 21, 34, etc. It's as easy as 3.1415.....
Whoa! There seems to be a whole lot of confusion here as to just what a
prime number is. Simply put, it is a number that can only (without
leaving a remainder) be divided by 1 and by itself. 2 is the only even
prime number, since all other even numbers are divisible by 2.
There's an easy procedure for producing the series--one that can even be
implemented with pebbles. You lay out a whole lot of pebbles in a row.
Then, starting with the 2nd pebble, you remove every 2nd pebble. After
that, you start with the third pebble and remove every 3rd pebble. Next
you go to the 5th pebble (you already removed the 4th) and remove every
5th pebble...and so on until you've removed all you can.
There's nothing mysterious about the series and it's not that hard for
even the most primitive peoples to stumble on it, as the above "game"
shows.
--
Dave Oldridge
doldridg@fox.nstn.ns.ca
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