Re: Computational complexity, number theory tidbits

From: C. Bond (cbond_at_ix.netcom.com)
Date: 08/04/04 

Date: Wed, 04 Aug 2004 15:04:45 GMT

James Harris wrote:

[snip]

> > Like to count the primes up to 10, you'd have
> >
> > 10 - [10/2] - [10/3] + [10/6] + 2 = 4
>
> OOPS! Knew the answer ahead of time, so I cheated and screwed up.
>
> That should be
>
> 10 - [10/2] - [10/3] + [10/6] + 2 - 1 = 4
>
> > and those primes, of course, are 2, 3, 5 and 7.
> >
> > Notice that you subtract all the evens, and then all the naturals that
> > have 3 as a factor, but you've over-subtracted in two ways, as 6 is
> > both even and has a factor of 3, so you subtractred for it twice, so
> > you add 1 back in, and then you add 2 in because you've subtracted for
> > 2 and 3 along the way.
>
> And you subtract 1 for 1, which gives you 4.
>
> Well that's what I get for taking shortcuts.

Then you have no business suggesting that others refrain from posting material whichdoes not stand up to
close scrutiny. Your own record in this respect is miserable.

> James "Often in error, but never in doubt." Harris 

--
There are two things you must never attempt to prove: the unprovable -- and the obvious.
--
Democracy: The triumph of popularity over principle.
--
http://www.crbond.com

Relevant Pages