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37 votes
3 answers
2k views

How to prove the identity $L(2,(\frac{\cdot}3))=\frac2{15}\sum\limits_{k=1}^\infty\frac{48^k}{k(2k-1)\binom{4k}{2k}\binom{2k}k}$?

For the Dirichlet character $\chi(a)=(\frac a3)$ (which is the Legendre symbol), we have $$L(2,\chi)=\sum_{n=1}^\infty\frac{(\frac n3)}{n^2}=0.781302412896486296867187429624\ldots.$$ Note that this ...
6 votes
1 answer
494 views

(Explicit) Tauberian theorems: removing $(\log x/n)$

Say that $\{a_n\}_{n\geq 1}$, $|a_n|\leq 1$, are such that $$\left|\sum_{n\leq x} a_n \log \frac{x}{n}\right|\leq \epsilon x\quad\text{for all $x\geq x_0$.}$$ What sort of bound can we deduce on $S(x)=...
4 votes
1 answer
213 views

Asymptotic behavior of weighted sums involving the fractional part function

Currently, I am studying the asymptotic behavior of sums of the form \begin{equation}\label{eq1}\tag{1} \sum_{k=1}^{n-1} f(n-k) \left\{ \frac{n}{k} \right\} \end{equation} In this context, based on ...
2 votes
0 answers
121 views

Solving a system of differential-like equations for reverse Euler-Maclaurin summation

Aim A particular instance of a rational zeries that has as of yet not been evaluated is: \begin{align} Z:= \sum_{n=1}^{\infty} \frac{\zeta(2n)}{(2n)!}. \label{EM1} \tag{EM1} \end{align} This sum ...
3 votes
2 answers
511 views

Exotic series for some mathematical constants from String Theory

Following these MO posts from Timothy Chow and Henri Cohen and their comments, based on Saha & Sinha's String Theory article, I have found three series for $\pi$, Apéry's constant $\zeta(3)$ and ...
7 votes
4 answers
793 views

Must bounded sequences be well-distributed to most *composite* moduli?

Let $\{a_n\}_{n=1}^N$, $|a_n|\leq 1$. Let $Q=\sqrt{N}$. Then $a_n$ is well-distributed modulo most prime $p\leq Q$, in the following sense: $$\sum_{p\leq Q} \frac{1}{p} \left(\frac{1}{N/p} \sum_{\...
2 votes
0 answers
157 views

What rational zeta series with non-integer arguments appear in mathematics?

Background Rational zeta series are series of the form $$\sum_{n=2}^{\infty} q_{n} \zeta(n + p, m), \label{1} \tag{1} $$ where $\zeta(x,m)$ is the Hurwitz zeta function and $q_{n}, \ p \in \mathbb{Q} \...
1 vote
1 answer
101 views

Finding $\lim_{n \to \infty} \sum_{k=2}^{n-2} \zeta(k) \zeta(n-k) x^{k-1} = x^{-1} - \psi_{0}(-x) - \gamma$ from the generating function of $\zeta(•)$

In equation (130) of this page, the identity $$\lim_{n \to \infty} \sum_{k=2}^{n-2} \zeta(k) \zeta(n-k) x^{k-1} = x^{-1} - \psi_{0}(-x) - \gamma \label{1} \tag{1} $$ is stated. Here, $\zeta(\cdot)$ is ...
2 votes
1 answer
161 views

Closed form expression for this zeta-like series involving GCD and LCM

I am looking for a closed form for this function $\Lambda:\mathbb{Q}^+\to\mathbb{R}^+$: $$\Lambda(q) = \sum_{m,n\geq 1}\left(\frac{q\wedge\frac{m}{n}}{q\vee\frac{m}{n}}\right)^\alpha\left(\frac{m \...
11 votes
3 answers
866 views

Conditions under which $\lim_{s\to1^+}\sum_{n=1}^{\infty}\frac{a_n}{n^s}=\sum_{n=1}^{\infty}\frac{a_n}{n}$

I was working with some Dirichlet series and I realized that I have never seen any general conditions under which \begin{equation} \sum_{n=1}^{\infty}\frac{a_n}{n}=\lim_{s\to1^+}\sum_{n=1}^{\infty}\...
7 votes
1 answer
332 views

A conjectured series expression for the Riemann $\xi$-function and/or Completed L-series. Could this be proven?

This post builds on an MSE question about a conjectured series expression for the Riemann $\xi$-function: $$\xi(s) = \xi(1-s) = \sum_{n=1}^\infty (-1)^{n+1}\,\big(\xi\left(s+in\right)+\xi\left(1-s+in\...
3 votes
4 answers
497 views

Asymptotic for Ramanujan's $\tau$-function

The Ramanujan's $\tau$-function is defined by $$q\prod_{n=1}^\infty (1-q^n)^{24}=\sum_{n=1}^\infty \tau (n)q^n$$ where $|q|\lt 1$. Is there a known asymptotic formula for $\tau (n)$ or $|\tau (n)|$, i....
2 votes
0 answers
131 views

Limit of scaled infinite sum with Dirichlet characters modulo 4: is it zero?

I am trying to get an asymptotic formula such as $$ L_4(s, n) \sim L_4(s) + \rho_n(s)\Lambda_n + \frac{\alpha(s)}{\sqrt{n}} + \frac{\beta(s)}{\sqrt{n\log n}}+\cdots$$ where $L_4(s, n)$ is the first $n$...
0 votes
1 answer
259 views

Finding a strictly increasing Collatz sequence of arbitrary length [closed]

Is there a formula to construct a Collatz (3x + 1) sequence of arbitrary length that is strictly increasing? Obviously one can do this with a strictly decreasing sequence by just taking $2^n$ but I ...
2 votes
1 answer
197 views

2D lattice sum with numerator

I've been struggling a bit with a double sum that arose as the trace of an operator: $$\sum_{(j,k)\in Z^2 \setminus (0,0)} \frac{(j+k)^n}{(j^2+k^2)^n},$$ where $n$ is an even natural number. Is there ...
24 votes
1 answer
2k views

Parity of the multiplicative order of 2 modulo p

Let $\operatorname{ord}_p(2)$ be the order of 2 in the multiplicative group modulo $p$. Let $A$ be the subset of primes $p$ where $\operatorname{ord}_p(2)$ is odd, and let $B$ be the subset of primes $...
1 vote
1 answer
96 views

On the behaviour for the quotient involving Fermat numbers of $\frac{\psi(F_m)}{F_m}$ where $\psi(x)$ denotes the Dedekind psi function

In this post we denote the Dedekind psi function as $\psi(m)$ for integers $m\geq 1$. This is an important arithmetic fuction in several subjects of mathematics. As reference I add the Wikipedia ...
1 vote
0 answers
187 views

$\lim_{x\to \infty} \left(\sum_{n\leq x} (\log n)^k/n - \int_1^x (\log t)^k/t\right) = \text{?}$

It is easy to see (by Euler-Maclaurin, say, or just by thinking of a graph) that $$\lim_{x\to \infty} \sum_{n\leq x} \frac{(\log n)^k}{n} = \int_1^x \frac{(\log t)^k}{t} + C + O\left(\frac{(\log x)^k}{...
4 votes
1 answer
219 views

Numbers $n$ whose representation as the product of two divisors require more digits than that of $n$

Note: Posting in MO since it was unanswered in MSE Let $f(x)$ be the number of digits in the decimal representation of $x$ e.g. $, f(0) = 1, f(1729) = 4$. If $n = ab$ then we can show that $f(ab) > ...
16 votes
1 answer
4k views

Order of magnitude of $\sum \frac{1}{\log{p}}$

Question: What is the order of magnitude of the following sum? $$ \sum_{\substack{p<n\\\text{$p$ prime}}} \frac{1}{\log{p}} $$ Additional information: Since $$ \sum_{\substack{p<n\\\text{...
5 votes
1 answer
435 views

Limit on a certain double sum

While working with multi-zeta functions, I encountered the below (experimental) value for a certain evaluation (in a limit sense). Notice first this well-known fact in context $$\sum_{n,m\geq1}\frac1{...
3 votes
0 answers
219 views

On partial sums of the Ramanujan sums

Let $n$ be a positive integer and $c_{m}(n)$ denote the $m^{th}$ Ramanujan sum at $n$. What is the best known estimate for $\sum_{m=1}^{N} c_{m}(n)$?
2 votes
0 answers
448 views

Conjecture: The sequence {$π(2n+1)!$} is equidistributed in the interval (0,1)

Let $n\in\mathbb{N}$. From the book "Uniform Distribution of Sequences" (available here) by L. Kuipers and H. Niederreiter, (from pg. 8) I found that for any irrational $\theta$, the ...
1 vote
1 answer
387 views

Under a condition, $\frac{1}{b } = \sum_{n=1}^{\infty}\frac{1}{a_{n}}$ will never happen

Conjecture: There is no $b,\{a_n\}_{n=1}^{\infty}$ such that $b,a_n \in \mathbb{N}^+, a_{n+1}\ge a_n$, $$\lim_{n\rightarrow \infty}\frac{a_{n+1}}{a_{n}}=\infty\qquad\text{and}\qquad\frac{1}{b}= \...
11 votes
2 answers
726 views

What can one say about $\sum\limits_{i=1}^\infty \frac{1}{p_{i+1}^2-p_i^2}$?

Denoting by $p_i$ the $i$-th prime, is it known that $\displaystyle \sum_{i=1}^\infty \frac{1}{p_{i+1}^2-p_i^2}$ converges? Can one compute a few digits based on euristic considerations or plausible ...
2 votes
0 answers
154 views

How can collections of rational zeta series that are equal to $\sum_{n=2}^{\infty} (\zeta(n) - 1)^{p} $ be obtained?

It has been discovered long ago that $$\sum_{n=2}^{\infty} \big(\zeta(n) - 1\big) = 1. \label{1} \tag{1} $$ More recently, a generalization of this result with binomial coefficients has been obtained: ...
2 votes
0 answers
162 views

Limit of infinite power tower $\lim_{n \rightarrow +\infty}\frac{a_0^{a_1^{a_2^{^{.^{.^{a_{n}}}}}}}}{b_0^{b_1^{b_2^{^{.^{.^{b_{n}}}}}}}}$

Let $\{a_n\}_{n \in \mathbb{N}}$ be a sequence of natural numbers. Let us define a function which roughly "make a tower of powers out of $\{a_n\}_{n \in \mathbb{N}}$", i.e. $$F:\mathbb{N}^{\...
1 vote
0 answers
78 views

Concerning the coefficient $[q^n]\sum_{n\ge1}\frac{(aq)^n}{(1-bq^n)^2}$

I posted this on MSE, and not even @ParamanandSingh could answer, so I thought I should post it here Background: While trying to answer this question, I came up with a question of my own. Let $|a|,|b|,...
4 votes
0 answers
924 views

What fraction of fractions does Cantor's famous sequence enumerate?

Cantor's famous sequence $\frac{1}{1},\frac{1}{2},\frac{2}{1},\frac{1}{3},\frac{3}{1},\frac{1}{4}, \frac{2}{3},\frac{3}{2},\frac{4}{1}, \frac{1}{5},\frac{5}{1},\frac{1}{6}, ...$ provides a ...
5 votes
1 answer
491 views

Is the parity of $\omega(n)$ equally distributed?

I recently learned that the prime omega function $\Omega(n)=\Omega\left(p_1^{\alpha_1}p_2^{\alpha_2}...p_k^{\alpha_k}\right)=\alpha_1+\alpha_2...+\alpha_k$ is very well studied. In particular, we know ...
2 votes
0 answers
422 views

Sequences with high densities of primes: how to boost them to get even more and larger primes

I propose a methodology to help find large prime numbers with a much higher probability than picking up random numbers and testing them for primality. This would help speed up prime number generators ...
6 votes
0 answers
257 views

Convergence with the recurrence $T_{n+1}=T_n^2-T_n+\frac{n}{p_n}$

For each integer $n\geq 1$ I define the recurrence $$T_{n+1}=T_n^2-T_n+\frac{n}{p_n},$$ with $T_1=1$, where $p_k$ denotes the $k$-th prime. So multiplying by $(-1)^n$ and telescoping gives that for ...
5 votes
0 answers
343 views

Can the inverse of the Riemann zeta function in $s > 1$ be expressed as a series?

In this post, we are interested in the Rimenann zeta function $\zeta(s)$ in $s > 1$ only where it is strictly decreasing rather than $s$ in the entire complex plane. We have the Stieltjes series ...
3 votes
0 answers
183 views

From Firoozbakht's conjecture to set interesting conjectures for sequences or series of primes

In this post we denote the $k-th$ prime number as $p_k$. I present two conjectures, the first about the asymptotic behaviour of a product and the other about an alternating series. I don't know if ...
2 votes
2 answers
385 views

What is the growth rate of the sum of powers of distinct primes closest to a given a integer?

Let $n$ be a positive integer, and $$2 = p_1 < p_2 < \dots < p_m \le n$$ be the sequence of all primes less than or equal to $n$. For each index $j$ let $p_j^{e_j}$ be the largest power of $...
11 votes
1 answer
497 views

Sign of the function $f(n)=\sum_{k=1}^n\frac{\mu(k)}{k}$

It is well-known that the Mertens function $M(n)=\sum_{k=1}^n\mu(k)$ changes sign infinitely many times when $n\rightarrow +\infty$. Let $f(n)=\sum_{k=1}^n\frac{\mu(k)}{k}$, then $\lim\limits_{n\...
2 votes
0 answers
167 views

What about series involving strong primes?

I know about the importance in analytic number theory of the sutdy of series involving prime numbers or constellations of prime numbers, for example, if I am not wrong, major theorems are Mertens' ...
0 votes
0 answers
89 views

Partial sums involving Gregory coefficients that cannot be an integer

For integers $n\geq 1$ let $G_n$ be the Gregory coefficients or reciprocal logarithmic numbers, see the Wikipedia [Gregory coefficients.] (https://en.wikipedia.org/wiki/Gregory_coefficients) $${z\...
1 vote
0 answers
86 views

Asymptotic behaviour of $\sum_{k=1}^{n}\frac{R_{k+1}+R_k}{R_{k+1}-R_k}$, where $R_k$ are the Ramanujan primes

I was inspired in the following post from this Math Overflow that was asked yerterday Asymptotic behavior of a certain sum of ratios of consecutives primes to ask about a similar question for ratios ...
0 votes
0 answers
85 views

Mean and logarithmic values for arithmetic function

Define the mean value for function $f$ as $\lim \limits_{x \to \infty} \frac{1}{x} \sum \limits_{n \leq x} f(n)$ if the limit exists denoted as $M_f$ Define the logarithmic value for function $f$ as $...
2 votes
0 answers
156 views

Questions about a certain sequence of naturals generated by primorials

I'm working on the following sequence of naturals (which is NOT listed in OEIS) $$3,5,11,17,23,29,59,89,119,149,179,209,419,629,839,1049,1259,1469,1679,...$$ whose elements are generated this way $$3=(...
1 vote
0 answers
190 views

Does there exist such a sequence $B$ when $p>5$?

Let $A = (a_1, a_2, \ldots, a_n)$ be the sequence of odd primes are less than or equal to a prime number $p$. Let $C$ be the infinite ascending sequence of composite numbers that their factors are ...
56 votes
1 answer
4k views

A mysterious connection between primes and $\pi$

The Prime Number Theorem relates primes to the important constant $e$. Here I report my following surprising discovery which relates primes to $\pi$. Conjecture (December 15, 2019). Let $s(n)$ be ...
3 votes
2 answers
1k views

On the Dirichlet series for $1/\zeta(s)$ for real $s$ and the zeros of zeta

For $\Re(s)>1$, it is well known that $$\frac{1}{\zeta(s)} = \sum_{n=1}^{\infty} \frac{\mu(n)}{n^s}$$ where $\mu$ denotes the Mobius function and $\zeta$ is the Riemann zeta function. I have heard ...
0 votes
0 answers
47 views

Approximation of $\sum_{\substack{n\geq 1\\n\text{ is abundant}}}\frac{\sigma(n)}{n^3}$, where $\sigma(n)$ denotes the sum of divisors function

Let $\sigma(n)=\sum_{1\leq d\mid n}d$ the sum of divisors function then, from the theory of Dirichlet series, it is well-known the value of $$\sum_{n=1}^\infty\frac{\sigma(n)}{n^3},$$ in terms of ...
6 votes
0 answers
97 views

Counterexamples or reasonings about the transcendence of series involving the Möbius function, and polynomials in the denominator

This afternoon I tried to read and understand some sections of the paper Some Applications of Diophantine Approximation by R. Tijdeman procedding from Number Theory for the Millenium III, A K Peters (...
4 votes
1 answer
244 views

The function $\sum_{n=0}^\infty\frac{(-1)^n\mu(2n+1)}{(2n+1)^s}$: reference request or particular values at integers and abscissa of convergence

We denote for integers $m\geq 1$ the Möbius function as $\mu(m)$. With the help of a CAS, Wolfram Alpha online calculator, I was calculating certain values of $$\sum_{n=0}^\infty\frac{(-1)^n\mu(2n+1)}{...
13 votes
3 answers
1k views

iterated harmonic numbers vs Riemann zeta

Define the $m$-th iterated harmonic sums in the manner: $\bar{H}_0(n):=1$ and for $m\geq1$ by $$\bar{H}_m(n):=\sum_{k=1}^n\frac{\bar{H}_{m-1}(k)}k.$$ For example, $\bar{H}_1(n)=\sum_{k=1}^n\frac1k$ ...
5 votes
1 answer
943 views

Are all the numbers $\pi(n^2)/n^2\ (n=1,2,3,\ldots)$ pairwise distinct?

For $x>0$ let $\pi(x)$ denote the number of primes not exceeding $x$. A well-known conjecture of Legendre states that $\pi(n^2)<\pi((n+1)^2)$ for any positive integer $n$. Here I ask the ...
7 votes
0 answers
1k views

A problem of Erdős on convergence of $\sum (-1)^nn/p_n$ and equidistribution of $\pi(n)$ modulo 2

Erdős asked1 whether the series $$\sum_{n=1}^\infty \frac{(-1)^n n}{p_n}$$ converges. Here, $p_n$ denotes the n-th prime. I can show that this series converges simultaneously with the series $\sum_{...