The average number of divisors of positive integers from 1 to n ...

Number Theory Level pending

The divisors of a positive integer, n, is defined as those positive integer equal to or greater to 1 and less than or equal to n that divide with a remainder of zero into n. The number of visors of n is count of the divisors of n. Note, 1 and n are always divisors of n and if those are the only divisors then n is either prime or 1. If n is 1, then the count of divisors is 1 as 1 and n are equal.

Define the average number of divisors of all positive integers from as t n \overline{t}_n .

For all positive integers, n n , what the maximum deviation of log e n \log_{\mathbb{e}} n to t n \overline{t}_n without considering whether this interval is an open or closed set?


The answer is 1.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

( 1 1 1 1 1 1 1 1 1 0 1 0 1 0 1 0 1 0 0 0 1 0 0 1 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 ) \left( \begin{array}{ccccccccc} 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\ 0 & 1 & 0 & 1 & 0 & 1 & 0 & 1 & 0 \\ 0 & 0 & 1 & 0 & 0 & 1 & 0 & 0 & 1 \\ 0 & 0 & 0 & 1 & 0 & 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 \\ \end{array} \right)

where the columns of the table have ones where the divisors are.

Let us read the table row-wise instead. The total number of divisors for the positive integers from 1 to n n is i = 1 n n i \sum _{i=1}^n \left\lfloor \frac{n}{i}\right\rfloor . The average therefore is 1 n i = 1 n n i \frac{1}{n}\sum _{i=1}^n \left\lfloor \frac{n}{i}\right\rfloor . The average is less then or equal to 1 n i = 1 n n i \frac{1}{n}\sum _{i=1}^n \frac{n}{i} where the error in each term being added is less than 1. This can be rewritten as i = 1 n 1 i \sum _{i=1}^n \frac{1}{i} . These are harmonic numbers. Therefore, H n 1 < t n H n H_n-1\lt \overline{t}_n \leq H_n . Comparing the upper and lower Riemann sums at positive integer boundaries to 1 n 1 t d t = l o g e n \int_1^n \frac{1}{t} dt=log_{\mathbb{e}} n gives log e n + 1 n < H n < log e n + 1 \log_{\mathbb{e}} n+\frac{1}{n}< H_n<\log_{\mathbb{e}} n+1 . In the limit as n n\to\infty , log e n < H n < log e n + 1 \log_{\mathbb{e}} n< H_n<\log_{\mathbb{e}} n+1 . In conclusion, t n log e n 1 \left|\overline{t}_n-\log_{\mathbb{e}} n\right|\leq 1 . A deviation of 1 is achieved at n = 1 n=1 .

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...