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Re: prime numbers and African artifact
Roy Lakin (roy@dsbc.icl.co.uk)
Thu, 13 Jul 1995 11:17:01 GMT
In article <3u0or7$qi7@pyrrhus-f.hrz.tu-chemnitz.de> vhe@informatik.tu-chemnitz.de (Volker Hetzer) writes:
>nickb@harlequin.co.uk (Nick Barnes) writes:
>
>:In article <rfJ0meEYsDj7075yn@fox.nstn.ns.ca> doldridg@fox.nstn.ns.ca
>:(Dave Oldridge) succumbs to a troll and attempts to describe the sieve
>:of Eratosthenes:
>:start:
>
>:1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
>
>:start at the second pebble and remove every 2nd pebble:
>
>:1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
>
>:start at the 3rd pebble and remove every 3rd pebble (watch carefully):
>
>:1 3 7 9 13 15 19 21 25 27 31 33 37 39 43 45 49 51 55 57 61 63 67 69 73 75
>
>:start at the, erm, 7th pebble and remove every 7th pebble:
>
>:1 3 7 9 13 15 21 25 27 31 33 37 43 45 49 51 55 57 63 67 69 73 75
>
>:etc, leaving you with this:
>
>:1 3 7 9 13 15 21 25 31 33 37 43 49 51 63 67 69 73 75
>Yeah, but shouldn't the sieve produce primes?
>9,15,21,25,27,33,49,51,63,69,75 are no primes.
>
>See you!
>Volker
These numbers were described by someone (Gardner?) as "lucky" numbers and
raised questions about which prime numbers were lucky and vice versa.
(The flaw in the sieve description is left as an exercise for the reader)
roy
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