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August 30th, 2014, 02:53 AM   #31
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Originally Posted by CRGreathouse View Post
(There's a side problem where my Internet connection has been lost, and I'm forced to post from places other than home. This means I don't have access to PARI/GP or my other specialized software. Hopefully the situation will be repaired next week.)
Very frustrating for you. No rush at my end.
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August 30th, 2014, 06:16 AM   #32
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Yes, very. In the meantime, would you check that my program is doing what you want? Otherwise the Inetnet plumbers could come and go without us being any further ahead than we are now.
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August 31st, 2014, 12:44 PM   #33
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Originally Posted by CRGreathouse View Post
Yes, very. In the meantime, would you check that my program is doing what you want? Otherwise the Inetnet plumbers could come and go without us being any further ahead than we are now.
I've had a go at a geometrical proof of this particular point here, which I think works?

Prime Numbers: Attempted proof

Bear in mind I'm only addressing the narrow point of whether the outputs from the function tend towards 1 in 2 (for level 1 numbers), 1 in 6 (for level 2 numbers) etc. And I'll acknowledge upfront that an error of even 1 is insufficient if we are attempting a 'counting' proof, but what I'm looking to discuss in the end is whether we could use this method in a different way that could lead to a reductio ad absurdum given the assumption that the conjecture is false.

Last edited by Hedge; August 31st, 2014 at 12:51 PM.
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September 1st, 2014, 01:05 AM   #34
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However, I would argue that it is stronger than a Poisson/binomial process since there is so much dependence and modular structure within the levels, meaning that the estimate is at least based on highly predictable frequencies, rather than independent probabilities.
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Originally Posted by CRGreathouse View Post
I assume that you can't prove this.
Just to explain, the previous quote was a response to this...
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September 6th, 2014, 06:11 AM   #35
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I said I'd look at the code

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Originally Posted by CRGreathouse View Post

Code:
f(p)={
  my(n=log(p)\log(2)+1,q=2^n-p,t);
  t=sum(i=0,#binary(q),if(bittest(q,i),q-=2^i;3^hammingweight(q)*2^i,0));
  (2^n-t)/3^hammingweight(2^n-p)
};
So far as I can see this bit (above) is right but lacks the restriction to q < 2^n/4

Quote:
Originally Posted by CRGreathouse View Post

Here's the code I'm using:
[code]ok(p)={
my(n=log(p)\log(2)+1,N=2^n,q=N-p,t,r);
if(N/4<=q&&q<N/2,return(0));
t=sum(i=0,#binary(q),if(bittest(q,i),q-=2^i;3^hammingweight(q)*2^i,0));
r=(2^n-t)/3^hammingweight(2^n-p);
denominator(r)==1&&r>0
};
Then you added the restriction above, which looks like it ought to work but there was a glitch that you noticed:

Quote:
Originally Posted by CRGreathouse View Post
looks like I forgot to check ok(k) in one place
Then, sorry but I can't work out what the last bit below does, which doesn't mean there is anything wrong with it, just that I can't follow the language well enough.

Quote:
Originally Posted by CRGreathouse View Post
Code:
cc(n)=my(v=List());while(n>1,listput(v,n);n=3*n+1;n>>=valuation(n,2));Set(v);

showcc(n)={
  while(n>1,
    print1(n" -> ");
    n=3*n+1;
    n>>=valuation(n,2)
  );
  print(1)
};

bad(n,v)={
  forstep(k=1,n-2,2,
    my(t=cc(k),u=setintersect(t,v));
    if(#u, showcc(k);v=setminus(v,u))
  );
  showcc(n)
};

v=[];forstep(n=1,1e6,2,if(ok(n),t1=setintersect(t=cc(n),v);if(#t1&&t1!=[5],bad(n,t1);print);v=Set(concat(v,t))))
Having said that, I now think there's a limit to the point of running this. While I was doing this attempted proof Prime Numbers: Attempted proof I realised a couple of things.

Firstly it convinced me that the proportion of level n integer outputs from the function do indeed tend up or down to 1 in 2(3^n)/3. (If you don't read it, the main point is that the function involves dividing by 3^n at level n. Every prime power (except powers of 2) has a primitive root; thus the multiplicative group of integers modulo 3n is cyclic. Thus we can arrange the level n inputs as a square/cube/cuboid grid that is cyclic every 2(3^n)/3 places - it's a bit more complicated as the pattern doesn't start out as a cuboid, but it tends to a pattern that can be filled with an increasing proportion of cuboids...)

Secondly it became more clear that the region over which this happens is pretty vast. 100 million < 2^21 and at this point the level 3 numbers are only just starting to tend down from about 1 in 19 towards 1 in 18 outputs. And for level 2 numbers we've tended down from 1 in 7 to 1 in 6.001 at about 2^6000. So running tests over 100 million or so wouldn't tell us a huge amount.

Last edited by Hedge; September 6th, 2014 at 06:29 AM.
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