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Questions where prime numbers play a key-role, such as: questions on the distribution of prime numbers (twin primes, gaps between primes, Hardy–Littlewood conjectures, etc); questions on prime numbers with special properties (Wieferich prime, Wolstenholme prime, etc.). This tag is often used as a specialized tag in combination with the top-level tag nt.number-theory and (if applicable) analytic-number-theory.

9 votes
Accepted

Covering the primes with pairs of consecutive integers

For large enough $n$ no such set of integers exist. First of all, let us say that $a$ covers prime $p$ if $a$ or $a+1$ is divisible by $p$. Now, if $p$ is a prime with $\frac{n+1}{2}<p\leq n$, $a\leq …
Alexander Kalmynin's user avatar
9 votes
Accepted

Condition for $8p+1$ divides $(2^p+1)/3$?

This follows easily from the octic reciprocity law for $2$. More precisely, it states that if $q$ is a prime of the form $q=8n+1$ and $n$ is odd, then $q=a^2+256b^2$ for some integers $a,b$ (note that …
Alexander Kalmynin's user avatar
1 vote

A special kind of multiplicative function $f: \mathbb N \to \mathbb N$ such that $f(p)=p+k$ ...

Suppose that the Schinzel's hypothesis is true. It suffices to assume that for any pair of coprime integers $a$ and $b$ with $a>0$ and such that $(a,b) \neq (c^2,-d^2)$ for any integers $c$ and $d$ th …
Alexander Kalmynin's user avatar
6 votes
Accepted

Estimating a sum over prime numbers

Using the fact that $$\sum_{y\leq p\leq 2y} \frac{\log p}{p}\ll 1,$$ we get for any $A\geq 2$ $$\sum_{x/2A\leq p\leq x/A} \frac{\log p}{p\log(x/p)}\ll \frac{1}{\log A}$$ Hence for any positive int …
Alexander Kalmynin's user avatar
19 votes
Accepted

Are there any papers about this observation of the distribution of the zeros of the zeta fun...

This is called Landau's formula. More precisely, if we extend the von Mangoldt function $\Lambda(n)$ to the function $\Lambda:\mathbb R_+\to \mathbb R$ by $\Lambda(x)=0$ for non-integer $x$, then $$ \ …
Alexander Kalmynin's user avatar
6 votes

Counting squares modulo $p$ that are also prime in an interval

Here is the paper by P. Pollack on the distribution of non-residues and residues. Theorem 1.3 states that for any $\varepsilon>0$, $A<\infty$ and large enough $m$ there are at least $(\ln m)^A$ prime …
Alexander Kalmynin's user avatar
8 votes
Accepted

Is it true that $\det\big[\sin 2\pi\frac{(j-k)^2}p\big]_{1\le j,k\le p-1}=-\frac{p^{(p-1)/2}...

We will use the notation $e_p(t)=\exp\left(\frac{2\pi it}{p}\right)$. First, let us show that for any $1\leq m\leq \frac{p-1}{2}$ there is an eigenvector of your matrix $A_p$ with eigenvalue $$ \lambd …
Alexander Kalmynin's user avatar
4 votes

Increasing sequences and Wieferich primes

I will focus on Q3. Let us evaluate $J(2^{2^n}+1)$. Denote $N=2^{2^n}+1$. Then $N-1=2^{2^n}$. Notice that $2^{2^{n+1}}\equiv 1 \pmod N$. Let $M=\frac{N-1}{2^{n+1}}=2^{2^n-n-1}$, which is an integer. W …
Alexander Kalmynin's user avatar
23 votes

Does the average primeness of natural numbers tend to zero?

The answer to Question 1 is "yes". To see this, notice that $s_n$ is at most square root of the average square of divisor, i.e. $$ s_n\leq \sqrt{\frac{\sum_{d\mid n}d^2}{\sum_{d\mid n} 1}}=\sqrt{\frac …
Alexander Kalmynin's user avatar
4 votes
Accepted

Robin's inequality and the zeros of the Riemann zeta function

It is well-known that the Riemann hypothesis implies $$ \theta(x)=x+O(\sqrt{x}\ln^2 x). $$ Therefore, under the Riemann hypothesis we have $$ \ln\theta(x)=\ln x+O\left(\frac{\ln^2 x}{\sqrt{x}}\right). …
Alexander Kalmynin's user avatar
3 votes

Is the abscissa of convergence of $s\mapsto\sum_{n>0}(ng_{n}/2)^{-s}$ known?

Obviously, abscissa of convergence is at most 1, because the series is dominated by the series for $\zeta(s)$. In fact, it is equal to 1. Indeed, assume that your series converges for some $s=1-\varep …
Alexander Kalmynin's user avatar
6 votes
Accepted

A generalization Bertrand's postulate

First of all, as mentioned by Random above, this is a very strong conjecture, because it is stronger than Legendre's conjecture. As far as I know, it is not known even if we assume the truth of Rieman …
Alexander Kalmynin's user avatar
7 votes
Accepted

Is this Goldbach conjecture related quantity equal to the number of Goldbach decompositions ...

This identity is false. To see that, notice first that $$ \sum_{p\leq \sqrt{2n-3}}a_p(n)=2\sum_{p\leq \sqrt{2n-3}}1-\sum_{\substack{p\leq \sqrt{2n-3}\\ p\mid n}}1=2\mathrm{ord}_C(n)-O(\ln n), $$ so $$ …
Alexander Kalmynin's user avatar
12 votes
Accepted

A consequence of Firoozbakht's conjecture?

Notice that $$ 1\leq \frac{\log p_{n+1}}{\log p_n}=1+\frac{\log(p_{n+1}/p_n)}{\log p_n}\leq 1+\frac{p_{n+1}-p_n}{p_n\log p_n}. $$ The last inequality is due to $\log(1+x)\leq x$ for $x\geq 0$. Now, fo …
Alexander Kalmynin's user avatar
1 vote

Asymptotic for a number theoretic sequence and its Dirichlet series' convergence

Your series is never absolutely convergent in any half-plane of the form $\mathrm{Re}\,s>\delta$ with $\delta<1$ and there is even no convergence in the case $\mathrm{Re}\,s=1$. To prove this, let us …
Alexander Kalmynin's user avatar

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