Re: [PrimeNumbers] Q
- --- Wes <6bullocks@...> wrote:
> take the first three primes.Not just a circle, a 'wheel'.
> multiply them together - 2*3*5 = 30
> Excluding these primes, and including the number 1 there is a symetry
> that appears if a circle is drawn with circumference 30 units
> As is probably well known, each combination of possible residues isThey are the 'totatives'. The number of them is the totient function, phi().
> represented for a total of (2-1)*(3-1)*(5-1) or 8. It is also
> probably obvious that these 8 combinations of residues repeat for
> each "30 circle" thereafter.
> So, here is the question: "What are the 8 numbers between 1 and 30
> that are indivisible by 2, 3 and 5?" is there a known way to list
> them? I was trying to say in my earlier posting that I do have a way
> and that is what I'll describe next.
You can only list the totatives of N or evaluate phi(N) if you know the
factorisation of N, or are prepared to work out the factorisation of N whilst
That's given you a few terms to google. I'd guess Eric Weisstein's Mathworld is
probably the best resource for this and related concepts.
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