Monday, August 10, 2020

Using Zeta Zeros to Count Factors (2)

We have seen in the last entry, with respect to the Riemann Zeta Function, how to calculate the accumulated frequency of odd factors up to a certain number n.
This frequency as we have seen approximates closely the corresponding frequency of all factors (odd and even) to n/2.

So for example, if n = 300, the accumulated frequency of all the odd factors of the natural numbers up to 300, approximates closely the corresponding frequency of all factors (odd and even) to 150. 

Is implies therefore that to approximate the accumulated frequency of the even factors to 300, we can thereby count the frequency of all factors from 151 to 300.

Now the accumulated frequency of all odd factors to 300 is 680 (excluding as in all cases the trivial case where 1 is a factor). And if we count all factors (odd and even to 150) we get 629. So the relative accuracy of our result here is 92.5%. So the all factor underestimates the odd factor total in this case. But the approximation steadily increases towards 100% (in relative terms) as we progressively increase the value of n.

Likewise the accumulated frequency of all even factors to 300 is 803. However if we now count the frequency of all factors (odd and even) from 151 to 300 we get 854.
So the relative accuracy of our result is here 94% with the all factor now overestimating the frequency of even factors. However, once again the approximation steadily increases towards 100% as we progressively increase the value of n.

Alternatively we could say that if t = 2πn the frequency of zeros to t/2 = πn approximates the corresponding accumulated frequency of all odd number factors to n.
Also the frequency of zeros t/2 to t approximates the corresponding frequency of all even number factors to n.

Illustrating further, as we saw in the last entry, the accumulated frequency of factors up to n (not containing 3 or multiples of 3) can be measured by counting all factors to 2n/3.
Therefore again where n = 300, the accumulated frequency of factors (not containing 3 or multiples of 3) to 300 can be approximated by counting all factors up to 200.

This likewise implies that the accumulated frequency of those factors (comprising 3 or multiples of 3) can be approximated by counting all factors from 201 to 300.   

The cumulative frequency of factors (other than those containing 3 or multiples of 3) to 300 = 1001. And the cumulative frequency of all factors to 200 = 913.
So the relative accuracy of this latter estimate = 91.2% which is an underestimate but gradually increases towards 100% (in relative terms) as n increases.

And the corresponding cumulative frequency of factors (that are 3 or multiples of 3) to 300 = 479. And the cumulative frequency of all factors from 201 to 300 = 570.
So the relative accuracy of this latter estimate is 84% which is an overestimate but which again will approach 100% (in relative terms) as n progressively increases.
Alternatively we could say that if t = 2πn the frequency of zeros to t/3 = (2π/3)n approximates the corresponding accumulated frequency of all number factors (that do not include 3 as a divisor) to n.
Also the frequency of zeros 2t/3 to t approximates the corresponding frequency of all number factors (that include 3 as a divisor) to n.

Then we also saw in the last entry that if we exclude all factors containing either 2 or 3 as factors that the cumulative frequency of all factors to n/3 gives a good approximation.
Therefore again with n = 300 the cumulative frequency of all factors to 100 provides an estimate of those factors to 300 (that exclude 2 or 3 as divisors).

The cumulative frequency of all factors (excluding 2 or 3 as divisors) to 300 = 403.
And the corresponding cumulative frequency of all factors to 100 = 382.
Therefore the relative accuracy is here 94.8% and approaches ever closer to 100% as n becomes progressively larger.

We can also approximate the cumulative frequency of all those factors (with 2 or 3 as divisors) to 300 through the corresponding calculation of all factors between 101 and 300.
Now the cumulative frequency of those factors (with 2 or 3 as divisors) to 300 = 1080.
And the cumulative frequency of all factors between 101 and 300 = 1101.
So the relative accuracy is here 98.1% and approaches ever closer to 100% as n progressively increases.

Alternatively we could say that if t = 2πn the frequency of zeros to 2t/3 = (4π/3)n approximates the corresponding accumulated frequency of all number factors (that do not include 2 or 3 as a divisor) to n.
Also the frequency of zeros t/3 to t approximates the corresponding frequency of all number factors (that include 2 or 3 as a divisor) to n.


In principle these ideas can be extended to any combination of factors.
For example say we want to approximate the accumulation of all factors (excluding 3, 7 or 11 as divisors) to n
Now the exclusion of factors containing 3 = 1/3 of divisors.
Then 1/3 of numbers divisible by 7 are also divisible by 3 so fractions divisible by both 3 and 7 = 1/3 + 2/3(1/7) = 7/21 + 2/ 21 = 9/21 = 3/7.

Then the fraction of numbers divisible by 3, 7 or 11 = 3/7 + 1/11(4/7)
= 33/77 + 4/77 = 37/77.

Therefore the fraction of natural numbers not divisible by 3, 7 or 11 = 40/77.

So to approximate the frequency of factors to n (that do not have 3, 7 or 11) as divisors, one accumulates all factors to (40/77)n.
Thus in the convenient case where n = 77, one would count the factors of all numbers to 40 = 118.
And the actual number of such factors to 77 = 131. So the relative accuracy is 90.1% Then to approximate those factors with 3, 7 or 11 as divisors, one would count all factors from 41 to 77 = 153.  And the actual number of such factors = 140. So the relative accuracy = 93.6%, which would improve towards 100% as n becomes progressively larger.

And as before one can use zeta zeros to approximate the answer in both cases.
So in the former case we would count the zeta zeros to 80π i.e. 251.3 = 109 with a relative accuracy = 83.2%.
Then in the latter case we would count the zeros from 80π to 154π, i.e. from 251.3 to 483.8 i.e. 261 109 = 152. Therefore the relative accuracy here = 99.3%.

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