```Date: Dec 7, 2012 9:16 AM
Author: Robert Hansen
Subject: Re: A Good Activity

I haven't seen this rule before but if you do just the first two iterations of the sieve of Eratosthenes you can see how this pattern arises.Bob HansenOn Dec 6, 2012, at 2:16 PM, Paul Tanner <upprho@gmail.com> wrote:> On Thu, Dec 6, 2012 at 11:06 AM, Robert Hansen <bob@rsccore.com> wrote:>> The other night, my son and I worked out all the primes less than 100.>> > > One of the "little theorems" or "tricks" on the primes that could come> in handy is that all primes greater than 3 are either 1 less or 1> greater than some multiple of 6 - the set of all primes greater than 3> is a subset of of the set of all positive integers 6c-1 or 6c+1 for> all positive integers c. (It makes it easier to recall all the primes> up to whatever number - just count up multiples of six and at each> count try to recall which of the two numbers in question are composite> and which of the two are prime.> > I wrote two messages using this fact with respect to primes at> sci.math about a decade ago, to share some things I found with respect> to the Twin Prime Conjecture:> > "Twin prime conjecture restated without reference to primes"> http://mathforum.org/kb/message.jspa?messageID=507327> > "Re: Twin prime conjecture restated without reference to primes"> http://mathforum.org/kb/message.jspa?messageID=507328
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