Questions tagged [prime-numbers]
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.
2,020
questions
5
votes
2
answers
1k
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Error term in Mertens' third theorem
Mertens' third theorem states that:
$$\prod_{\substack{
p \leq x \\
\text{p prime}
}} \left( 1 - \dfrac{1}{p} \right) \sim \dfrac{e^{-\gamma}}{\log(x)}$$
Question: what is the best functions (...
3
votes
0
answers
79
views
Are numbers which are the product of n primes more common than numbers which are the product of n-1 primes? [duplicate]
In a recent video (https://www.facebook.com/188916357807416/videos/519169035700435/) Stephen Wolfram wonders whether, for every integer n>2, eventually the number of integers which are precisely the ...
4
votes
1
answer
269
views
Reference / Survey for finite field analog number theory
It is folklore that many number theoretic results on prime numbers have a simpler-to-prove finite field analog. For example, on the one hand, the proof of the Prime Number Theorem
$$\#\{\text{prime ...
6
votes
1
answer
855
views
How to explain this prime gap bias around last digits?
My question is related to this article by Oliver and Soundararajan (article about a bias in the distribution of the last digits of consecutive prime numbers).
After trying some python experimental ...
1
vote
1
answer
131
views
Another kind of primality related to tessellations by polygons
You can define a number $p$ to be prime by "no tessellation of $p$ identical squares forms a convex figure". This suggests what I'll call a t-prime $p$, defined by "no tessellation of $p$ identical ...
0
votes
0
answers
90
views
Set of primes $p_{1}\equiv 3 \bmod p_{2}$ such that $\phi(2^{\frac{{p_1}-3}{p_2}}-1)\equiv 0 \bmod p_1$ with $p_1,p_2\equiv 3\bmod 4$?
let $p_1$ and $p_2$ be positive primes such that $p_1,p_2 \equiv 3\bmod 4$
and $\phi$ is the Euler totiont function , I want to find the Set of primes $p_{1}\equiv 3 \bmod p_{2}$ such that $\phi(2^...
2
votes
1
answer
225
views
How does one prove that the density of unusual numbers is $\ln 2$?
The Wikipedia page for unusual number states that the density of that set is $\ln 2$, and that this was proven by Schroeppel in 1972. The only source that I found for that is the HAKMEM document, and ...
4
votes
1
answer
211
views
Primes in arithmetic progressions above a given threshold
Given co-prime $a,b$, Dirichlet's theorem states that there are infinitely many primes in the arithmetic progression $M = \{ a + bn : n \in \mathbb N\}$. Linnik's theorem asserts that the first such ...
1
vote
1
answer
352
views
Equation of the Chebyshev $\psi$ function
Consider $\Psi(x)$ to be the Chebyshev function given by
$$\Psi(x)=\sum_{n\leq x} \Lambda(n)$$
where $\Lambda(n)$ is the Mangoldt function which is equal 0 unless $n $ is prime power, and let $(E)$ ...
1
vote
0
answers
102
views
Write $p^2$ as $x^2+2y^2+3\times 2^z$ with $x,y,z$ nonnegative integers
In April 2018, I noted that the first integer $n>1$ with $n^2\not\in\{x^2+2y^2+3\times 2^z:\ x,y,z=0,1,2,\ldots\}$ is $$5884015571=7\times17\times49445509.$$
Question. Is it true that for each ...
-1
votes
1
answer
137
views
Sufficient conditions on $ a_i,b_i$ for $a_1\phi(n)+b_1, \cdots, a_k\phi(n)+b_k$ to be simultaneously prime infinitely often?
I am really interested in sufficient conditions on $a_i, b_i$ guaranteeing that the linear forms $a_1\phi(n)+b_1,\dots, a_k\phi(n)+b_k$ become simultaneously prime for infinitely many positive ...
2
votes
0
answers
81
views
quadratic residues and cubic polynomials [closed]
I'm really not sure about this, but I've heard somewhere that for any prime $p$,
$|\sum_{x=0}^{p-1} (\frac{ax^3 +bx^2 +cx +d}{p} ) |\le \sqrt{2p}$ holds.
Does anyone know a proof for this inequality ...
7
votes
1
answer
1k
views
Some interesting experimental results about the distribution of primes
Let's consider the following metric of the gap between consecutive primes
$$m(k)=\frac {p_k^2-p_{k-1}^2} {24}\;\;\;\;\;(k\ge4)$$
Now, let's define the function
$\delta(k)=m(k)\;\;\;\;$ if $\,m(k)\,$ ...
2
votes
1
answer
152
views
Sequence of least prime-multiples with smallest Hamming weight
It is known that
Almost all primes have a multiple of small Hamming weight, which makes me wonder what is known about the least multiples of primes that have least Hamming weight.
Questions:
what ...
0
votes
0
answers
128
views
A quadratic trinomial that generates only prime numbers of the form $4m+1$
It is known that Euler's polynomials $\,n^2+n+p\,$ ($p\,$ prime) represent a prime for $\,n=0,\,...,\,p-2\,$ if and only if the field $\,Q (\sqrt{1-4p})\,$ has class number $\,h=1$.
The best ...
6
votes
1
answer
227
views
Is there a connection between the average 'compositeness' of a rational number and $\phi$ (golden ratio)?
Let $n\in N$, where $n = p_{1}^{k_{1}}p_{2}^{k_{2}}...p_{m}^{k_{m}}$ for $p_{i}$ prime.
Define the 'density' of $n$ as:
$d(n) = \frac{(p_{1}+1)^{k_{1}}(p_{2}+1)^{k_{2}}...(p_{m}+1)^{k_{m}}}{n}$
...
0
votes
1
answer
159
views
does the ratio of the count of rational numbers on an $n\times n$ grid to $n^2$, converge as $n$ tends to infinity [closed]
Suppose we order the rational numbers using the diagonal method (used to prove they are countable) using an $n\times n$ grid. Now suppose we count the distinct rational numbers (those points on the ...
0
votes
1
answer
237
views
What can this $\int_{0}^{t} (\pi(x)-Li(x)) dx$ tell us about primes distribution?
Many papers I have read which are related to primes distribution only it discussed sign and refinement Bounds of $\pi(x)-Li (x)$ with $\pi(x)$ is a prime counting function and $Li (x)$ is the ...
1
vote
1
answer
188
views
Resolution of an inequality on integers
I’m trying to resolve respect to $k$ the following inequality,
$$
k\left(\log k +\log \log k-\alpha+O\left(\frac{\log \log k}{\log k}\right)\right)\geq x,
$$
in order to obtain, under the condition $...
1
vote
0
answers
142
views
About the distribution of Fibonacci numbers that are primes
Let's consider the Fibonacci sequence, that is the sequence of naturals defined by:
$F_1=F_2=1$
$F_{n+1}=F_{n}+F_{n-1}$
It is an open problem whether the sequence contains an infinite number of ...
4
votes
0
answers
143
views
Moments of the prime counting function given the moments of the second Chebyshev function
I have read this article (Montgomery and Soundararajan: Primes in short intervals. http://arxiv.org/abs/math/0409258 ). In the second page of the article, it is stated that the mean and variance of $\...
3
votes
1
answer
176
views
About the sum $S(p_n)=\sum_{1\le k\lt n}\,p_n\mod\;p_k$
For $\,p_n\gt2\,$ let's define the sum $\,S(p_n)=\sum_{1\le k\lt n}\,p_n\;mod\;p_k$, where $\,p_k\,$ represents the $\,k$-th prime.
The first terms of the sequence $\,S(p_n)\,$ (OEIS A033955 - sum of ...
1
vote
0
answers
175
views
Given a prime $\,p\ne3$, is it always possible to find another prime q such that $\,\phi(q)=\phi(p\cdot2^{2n+1})\,$ for some $n\in\mathbb{N}$?
Given a prime $\,p\ne3$, is it always possible to find another prime q such
that $\,\phi(q)=\phi(p\cdot2^{2n+1})\,$ for some $n\in\mathbb{N}$ ($\,\phi\,$ is the Euler's totient function)?
Some ...
3
votes
1
answer
310
views
Why is this sequence a good prime-generator?
For $n \in \mathbb N$ we can observe the $n$ remainders $b_1,...,b_n$ by writing $n$ as $n=a_k \cdot k+b_k$ for $1 \leq k \leq n$.
Because of the familiar division-with-remainder theorem we have $0 \...
7
votes
1
answer
493
views
About semiprimal representations of $1$
Conjecture $A_1$ : For every $m \in \mathbb N \setminus \{1\}$ there exist mutually different primes $p_{r_1},...,p_{r_m}$ and mutually different primes $b_{w_1},...,b_{w_m}$ and numbers $i_1,...,i_m \...
-1
votes
1
answer
281
views
Is it possible to determine whether the sequence $\,a_0=p,\;a_{n+1}=(a_n-2)\cdot a_n+2\,$ will reach another prime number?
Given a prime $\,p\,$ let's consider the following sequence:
$a_0=p$
$a_{n+1}=(a_n-2)\cdot a_n+2$
Is it possible to determine whether the sequence $\,a_n\,$ will reach, sooner or later, another ...
11
votes
1
answer
421
views
How many numbers $\le x$ can be factorized into three numbers which form the sides of a triangle?
Note: Posting in MO since it was unanswered in MSE
Definition: We say that a natural number $n$ has triangular divisors if it has at least one triplet of divisors $n = d_1d_2d_3, 1 \le d_1 \le d_2 \...
0
votes
0
answers
141
views
Given $\,m=\prod_k {p_k}^{\alpha_k}\,$ and the function $\,g(m)=\sum_k \alpha_k(p_k-1)^2$, find all solutions of the equation $\,g(2n)=n$
Let's consider the unique decomposition of a natural number $\,m\,$ into its prime factors:
$$\prod_k {p_k}^{\alpha_k}$$
Then, let's define the following arithmetic function (completely additive) $\,g:...
13
votes
1
answer
1k
views
About the number of primes which are the sum of 3 consecutive primes (OEIS A034962)
I made some numerical simulations about the number of primes which are the sum of 3 consecutive primes (OEIS A034962), that is for instance:
$$5+7+11=23$$
$$7+11+13=31$$
$$11+13+17=41$$
$$17+19+23=59$$...
1
vote
1
answer
116
views
Sequences of positive integers $(a_{k})_{k \in \omega}$ that only give finitely many zeros modulo $p_{k}$ in total for all polynomials
Let $(a_{k})_{k \in \omega}$ be a sequence of positive integers such that $a_{k} < p_{k}$, $a_{k} \leq a_{k+1}$ and $\lim_{k \rightarrow \infty} a_{k}=\infty$ where $p_{k}$ is the k-th prime ...
2
votes
0
answers
170
views
Funny questions about Moebius Function
I need to firstly claim that my research is not about number theory, however, I am pretty interested in it, especially funny questions in number theory, e.g. Kollatz Conjecture. Three years ago, I ...
0
votes
0
answers
77
views
Construction of (general class of) function(s), which sieves out primes, w.r.t. given conditions:
Consider the function $F(x)$ defined in following manner:
$F(n)$ is finite (likely $F(x)\in[0,1]$) if $n$ is prime and zero otherwise:
It has to satisfy following conditions:
(1) $F(x)$ is ...
3
votes
1
answer
266
views
Solutions in primes of the equation $\,3p^2+q^2=r^2+3$
Let's consider the Diophantine equation $\,3p^2+q^2=r^2+3$.
Actually, I am interested only in the solutions represented by sets $\,(p,q,r)\,$ of prime numbers.
It's easy to prove that if $\,(p,q)\,$ ...
4
votes
1
answer
313
views
Estimating certain short Kloosterman sums
Recall that for the classical Kloosterman sum
$$ K(a,b,p^t):= \sum_{x \in (\mathbb{Z}/ p^t \mathbb{Z})^* } \psi \left(\frac{ax+bx^{-1}}{p^t} \right),$$
where $\psi(x)=e^{2\pi ix}$, $a,b,t$ are natural ...
2
votes
1
answer
161
views
Numerical estimates for a function relating to twin primes :
Consider the following function :
$$F(s)= \sum_{\text{$p,\ p+2$ are primes}} \left({\frac{1}{p^s}}+{\frac{1}{(p+2)^s}}\right).$$
Brun's theorem tells us that $F(1)$ is finite.
We are looking for ...
7
votes
2
answers
905
views
Regularizing the sum of all primes
In the spirit of a similar question for the harmonic series, is there a way to regularize the (divergent) sum of all primes?
$$ \sum_{p \text{ prime}} p $$
Neither of these questions obtained a ...
1
vote
2
answers
141
views
Is the abscissa of convergence of $s\mapsto\sum_{n>0}(ng_{n}/2)^{-s}$ known?
The famous Polignac conjecture posits that the $n$-th prime gap $g_{n}:=p_{n+1}-p_{n}$ attains all even positive integral values infinitely many times, which implies $\displaystyle{\zeta_{Pol}:=s\...
2
votes
1
answer
525
views
Sets of primes with a given Frobenius conjugacy class
Let $a$ and $b$ be two relatively prime positive integers. Denote by $S$ the set of all positive primes of the form $a+bn$ (where $n$ is an integer, possibly zero or negative). Let $S'$ be any set of ...
2
votes
0
answers
156
views
Questions about a certain sequence of naturals generated by primorials
I'm working on the following sequence of naturals (which is NOT listed in OEIS)
$$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=(...
2
votes
0
answers
119
views
On the set $\{n>0:\ n\ \text{is a quadratic nonresidue modulo the}\ n\text{th prime}\}$
Let $S$ denote the set of positive integers $n$ with $n$ a quadratic nonresidue modulo the $n$th prime $p_n$. The first 20 elements of $S$ are
$$2,\, 3,\, 6,\, 7,\, 8,\, 10,\, 11,\, 13,\, 15,\, 18,\, ...
0
votes
1
answer
352
views
A sufficient condition for a set of primes to be the set of reducibility of an integer polynomial
Let $P$ be the set of all positive primes. Let $S$ an arbitrary infinite subset of $P$ satisfying the following assumption: there exists a finite Galois extension $K$ of $\mathbb{Q}$ and a conjugacy ...
0
votes
1
answer
132
views
A density zero set of primes dividing the values of a non-constant integer polynomial
For a given $P\in \mathbb{Z}[x]$ call a positive prime $p$ good if there exists $n\in \mathbb{Z}$ such that $p$ divides $P(n)$. Does there exist a non-constant $P$ such that the set of good primes has ...
5
votes
1
answer
164
views
Representation of primes of the form $4m+3$ with double radicals
Let $\,q\,$ be a prime of the form $\,4\, m_q+3$.
I ask if it is always possible to find two primes $\,p_1$ and $\,p_2$ of the form $\,4\, m_p+1$ such that
$$q=\sqrt{p_1+\sqrt{p_2+q}}$$
E.g.
$$3=\...
2
votes
1
answer
289
views
Convergence of series $\sum_{k=1}^{\infty}\frac{p_{k+1}-p_k}{(p_{k+1}+p_k)^\alpha}$
I ask if the series
$$\sum_{k=1}^{\infty}\frac{p_{k+1}-p_k}{(p_{k+1}+p_k)^\alpha}$$
where $p_k$ stands for the prime of index $k$,
has the same properties of convergence of the series $$\sum_{k=1}^{\...
-1
votes
1
answer
242
views
A conjecture about an inequality that involve Ramanujan primes
In this post we denote for integers $n\geq 1$ the $n$-th Ramanujan prime as $R_n$ (thus the sequence A104272 from the On-Line Encyclopedia of Integer Sequences), I add a conjecture that I think can be ...
-3
votes
1
answer
178
views
Asymptotic behavior of $\sum_{k=1}^{n}\frac{p_{k+1}}{p_{k+1}-p_k}$
I refer to my previous question Asymptotic behavior of a certain sum of ratios of consecutives primes.
We can split the sum
$$\sum_{k=1}^{n}\frac{p_{k+1}+p_k}{p_{k+1}-p_k}$$
where $p_k$ stands for the ...
10
votes
1
answer
465
views
Asymptotic behavior of a certain sum of ratios of consecutives primes
I am looking for the asymptotic growth of the following sum
$$\sum_{k=1}^{n}\frac{p_{k+1}+p_k}{p_{k+1}-p_k}$$
where $p_k$ stands for the prime of index $k$.
Manual computations show, for small values ...
6
votes
3
answers
821
views
Is it possible to multiply two series to get as a result all composite numbers?
I was toying with the following problem:
Is it possible to find two infinite integer sequences $(a_n), (b_n)>0$ such that $\sum_{n=1}^{\infty}\frac{1}{(a_n)^s}\cdot \sum_{n=1}^{\infty}\frac{1}{(b_n)...
6
votes
0
answers
197
views
Smooth integers with lower bound on $\omega(n)$
Define $(b,c)$-smooth integers to be integers having all prime factors bigger than $c$ and smaller than $b$.
Probability a number is $(b,1)$-smooth is governed by the Dickman function while ...
9
votes
1
answer
415
views
Conjectured primality test for specific class of $N=4kp^n+1$
Can you provide a proof or counterexample for the following claim?
Let $P_m(x)=2^{-m}\cdot((x-\sqrt{x^2-4})^m+(x+\sqrt{x^2-4})^m)$ .
Let $N= 4kp^{n}+1 $ where $k$ is a positive natural number , $...