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About the asymptotics of LCM

Let $g(x,c)$ be a uniformly random integer in the range $(x,x+c)$ and $LCM[x_1,x_2...x_i]$ the lowest common multiple of the integers $x_i$. A) Does the limit of (the asymptotics of $LCM[g(3^1,c),g(...
hakuna's user avatar
  • 61
11 votes
1 answer
1k views

What might the (normalized) pair correlation function of prime numbers look like?

Cross-posting from Math.Stackexchange. You might have read about the fortuitous meeting between Montgomery and Dyson. The background is that the nontrivial zeros of the Riemann zeta function, when ...
anon's user avatar
  • 441
8 votes
3 answers
1k views

Asymptotics for primality of sum of three consecutive primes

We consider the sequence $R_n=p_n+p_{n+1}+p_{n+2}$, where $\{p_i\}$ is the prime number sequence, with $p_0=2$, $p_1=3$, $p_2=5$, etc.. The first few values of $R_n$ are: 10, 15, 23, 31, 41, 49, 59, ...
Raj 's user avatar
  • 93
21 votes
3 answers
6k views

Why is the Chebyshev function relevant to the Prime Number Theorem

Why is the Chebyshev function $\theta(x) = \sum_{p\le x}\log p$ useful in the proof of the prime number theorem. Does anyone have a conceptual argument to motivate why looking at $\sum_{p\le x} \log ...
user16557's user avatar
  • 1,533
2 votes
0 answers
292 views

Prime divisors of the difference set

Fix $c\in(0,1)$, and let $N$ be a (large) positive integer. Given a set $A=\{0=a_1<\dots<a_n=N\}$ of density $\alpha:=n/N>c$ with $\gcd(A)=1$, I want to find a prime dividing as few ...
Seva's user avatar
  • 23k
4 votes
1 answer
708 views

Calculating the constant in the Bateman-Horn-Stemmler conjecture

Bateman & Horn [1], building on Bateman & Stemmler [2], give a conjectured formula for the density of numbers that produce simultaneous primes in a number of fixed polynomials. The constant ...
Charles's user avatar
  • 9,114
4 votes
2 answers
323 views

Multiplicity one prime in the factorisation of p-N

I'm wondering if analytic number theorists can prove results which have the following flavor: So let $N$ be a large positive integer. Q: Can you always find a prime number $p$ in the interval $(N, ...
Hugo Chapdelaine's user avatar
20 votes
2 answers
1k views

Median largest-prime-factor

Let $P(n)$ denote the largest prime factor of $n$. For any integer $x\ge2$, define the median $$ M(x) = \text{the median of the set }\{P(2), P(3), \dots, P(x) \}. $$ Classical results of Dickman and ...
Greg Martin's user avatar
  • 12.8k
12 votes
2 answers
616 views

Are there any notion of 'almost primes' known to have small gaps?

A notorious question with prime numbers is estimating the gaps between consecutive primes. That is, if $(p_n)_{n \geq 1}$ is the canonical enumeration of the primes, then set $g_n = p_{n+1} - p_n$. It ...
Stanley Yao Xiao's user avatar
17 votes
2 answers
1k views

Chen's Theorem with congruence conditions.

I would like to revisit a closed question of asterios in a more MO kind of way, because it cuts quite close to a related question about sieving that might be of general interest. The original ...
user avatar
12 votes
1 answer
867 views

Analytic lower bounds on the first sign change of pi(x) - li(x)?

There have been many results on the first sign change of $\pi(x)-{\mathrm{li}}(x)$: among others, Lehman, te Riele, Bays & Hudson, Demichael, Chao & Plymen, and most recently Saouter & ...
Charles's user avatar
  • 9,114
2 votes
0 answers
318 views

Pierpont primes

A Pierpont prime is a prime $p$ that can be written as $$p=2^u 3^v + 1.$$ What is known about Pierpont primes? I'm not a number theorist, and the best I can find is http://en.wikipedia.org/wiki/...
Thomas S's user avatar
5 votes
3 answers
3k views

Asymptotics of Product of consecutive primes

I am looking for the asymptotic growth of product of consecutive primes. Is there anything that is known about this growth?
Turbo's user avatar
  • 13.9k
3 votes
1 answer
708 views

Asociated sum series of the Euler Product over the Twin Primes?

Please consider the (presumably infinite) Euler product over the twin primes: $$ f(z) = \prod_{p\in\mathbb{P}}^{\infty} \Big( 1 - \frac{1}{(p(p+2))^ z} \Big) $$ (in which $p(p+2)$ is a divisor of $4((...
Max Lonysa Muller's user avatar
7 votes
0 answers
709 views

"probabilistic" density of primes?

A certain set $\cal P$ of primes is defined by two assumedly independent conditions: The first condition on a prime $p$ can be characterized in terms of the type of splitting of $p$ in certain Galois ...
Andrea Mori's user avatar
18 votes
3 answers
2k views

A question on the prime divisors of p-1

For each positive integer n we may define the convergent sum $$ s(n)=\sum_{p}\frac{(n,p-1)}{p^2} $$ where the summation is over primes p and $(a,b)$ denotes the greatest common divisor of a,b. It is ...
Dr. Pi's user avatar
  • 3,062
0 votes
1 answer
284 views

Do the roots of R(x) have any significance for the prime counting function?

I'm calculating the roots of the function \begin{equation} R(x) = \sum_{k=1}^{\infty}\frac{\mu(k)}{k}li(x^{1/k}) \end{equation} This function seems to have a largest and smallest positive root. Can ...
alext87's user avatar
  • 3,217
5 votes
2 answers
751 views

Proof in the literature of an equality involving the prime counting function

Let \begin{equation} R(x) = \sum_{k=1}^{\infty}\frac{\mu(k)}{k}li(x^{1/k}) \end{equation} where $\mu$ is the Mobius function and \begin{equation} li(x) = \int_0^x \frac{dt}{\log t} \end{equation} Is ...
alext87's user avatar
  • 3,217
4 votes
2 answers
577 views

What does the probabilistic model suggest the error term in the PNT should be?

Let $\Lambda(n)$ be the von Mangoldt function. The prime number theorem is equivalent to the statement that $\sum_{n \leq N} \Lambda(n) \approx N$. Defining $\lambda_{*}(n)= \Lambda(n)-1$ we may ...
Mark Lewko's user avatar
4 votes
2 answers
1k views

Product over the primes

I'm trying to estimate the product $$\prod_{p\lt q\lt r\lt s}1-\frac{24}{(pqrs)^2}$$ where $p,q,r,s$ are primes. This is for the purpose of calculating the density of Sloane's A070284 [1]. The idea ...
Charles's user avatar
  • 9,114
25 votes
7 answers
3k views

Question on consecutive integers with similar prime factorizations

Suppose that $n=\prod_{i=1}^{k} p_i^{e_i}$ and $m=\prod_{i=1}^{l} q_i^{f_i}$ are prime factorizations of two positive integers $n$ and $m$, with the primes permuted so that $e_1 \le e_2 \cdots \le e_k$...
David Corwin's user avatar
  • 15.4k
4 votes
2 answers
1k views

Calculating the infinite product from the Hardy-Littlewood Conjecture F

The Hardy-Littlewood Conjecture F [1] involves the infinite product $$\prod\left(1-\frac{1}{\varpi-1}\left(\frac D\varpi\right)\right)$$ where $\varpi$ ranges over the odd primes and $\left(\frac D\...
Charles's user avatar
  • 9,114
42 votes
2 answers
9k views

Is Li(x) the best possible approximation to the prime-counting function?

The Prime Number Theorem says that $\lim_{n \to \infty} \frac{\pi(n)}{\mathrm{Li}(n)} = 1$, where $\mathrm{Li}(x)$ is the Logarithm integral function $\mathrm{Li}(x) = \int_2^x \frac{1}{\log(x)}dx$. ...
Sam Derbyshire's user avatar
4 votes
1 answer
3k views

Is there another proof for Dirichlet's theorem? [duplicate]

Possible Duplicate: Is a “non-analytic” proof of Dirichlet’s theorem on primes known or possible? Dirichlet's theorem on primes in arithmetic progression states that there are ...
Hashem sazegar's user avatar
16 votes
4 answers
2k views

Who first proved that there are at least n^(1-ε) primes up to n?

It's well-known that Hadamard and de la Vallée-Poussin independently proved the Prime Number Theorem in 1896: that $\pi(n)=n/\log n+o(n/\log n)$. I'm curious as to a weaker result: that for any $\...
Charles's user avatar
  • 9,114
62 votes
1 answer
14k views

Is the Green-Tao theorem true for primes within a given arithmetic progression?

Ben Green and Terrence Tao proved that there are arbitrary length arithmetic progressions among the primes. Now, consider an arithmetic progression with starting term $a$ and common difference $d$. ...
Akela's user avatar
  • 3,699
10 votes
3 answers
3k views

A number encoding all primes

This may be a soft question, but it's just something I thought of one night before sleeping. It's not my field at all, so I am just asking out of curiosity. Has anyone studied the number which is the ...
David Carchedi's user avatar
12 votes
3 answers
929 views

Mertens-like sum in arithmetic progressions

I find myself needing a good estimate for $\sum_{p\le x,\, p\equiv a\bmod q} 1/p$, perhaps something like $$ \sum_{p\le x,\, p\equiv a\bmod q} \frac1p = \frac{\log\log x}{\phi(q)} + b(q,a) + O\big(\...
Greg Martin's user avatar
  • 12.8k
7 votes
4 answers
1k views

Reference for the expected number of prime factors of n larger than n^alpha is -log alpha

Let $0 < \alpha < 1$ be a constant. The expected number of prime factors of a "random" integer near $n$ which are greater than $n^\alpha$ is $-\log \alpha$. It's my understanding that (...
Michael Lugo's user avatar
69 votes
4 answers
14k views

Is a "non-analytic" proof of Dirichlet's theorem on primes known or possible?

It is well-known that one can prove certain special cases of Dirichlet's theorem by exhibiting an integer polynomial $p(x)$ with the properties that the prime divisors of $\{ p(n) | n \in \mathbb{Z} \}...
Qiaochu Yuan's user avatar
30 votes
3 answers
4k views

Heuristic argument for the prime number theorem?

Here is a bad heuristic argument for the prime number theorem. Let $n$ be a positive integer and assume that PNT holds up to $n$. Then $n$ itself is prime if and only if for each prime $p<n$ the ...
gowers's user avatar
  • 29k
20 votes
4 answers
3k views

Primes $p$ for which $p-1$ has a large prime factor

What are the best known density results and conjectures for primes $p$ where $p-1$ has a large prime factor $q$, where by "large" I mean something greater than $\sqrt{p}$. The most extreme case is ...
Vipul Naik's user avatar
  • 7,320
18 votes
2 answers
2k views

Primes of the form a^2+1

The fact that the Riemann zeta function $\zeta(s)$ and its brethren have a pole at $s=1$ is responsible for the infinitude of large classes of primes (all primes, primes in arithmetic progression; ...
Franz Lemmermeyer's user avatar
7 votes
2 answers
564 views

Smallest k-term AP of primes

Let $S(k)$ denote the smallest integer such that there exists a k-term arithmetic progression of primes among the integers $[1,S(k)]$. Green and Tao have an unpublished note that gives a very large ...
Mark Lewko's user avatar
8 votes
1 answer
721 views

Integral of the error estimate in the prime number theorem

This seems like something that should be in discussed in the literature, but I can't find anything. Here $\pi(x)$ is the prime counting function and $\psi(x)$ is the usual sum of the Von Mangoldt ...
Mark Lewko's user avatar
8 votes
4 answers
1k views

Prime numbers $p$ not of the form $ab + bc + ac$ $(0 < a < b < c )$ (and related questions)

If we ask which natural numbers n are not expressible as $n = ab + bc + ca$ ($0 < a < b < c$) then this is a well known open problem. Numbers not expressible in such form are called Euler'...
Jernej's user avatar
  • 3,463
15 votes
3 answers
1k views

Does there exist a meromorphic function all of whose Taylor coefficients are prime?

More precisely, does there exist an unbounded sequence $a_0, a_1, ... \in \mathbb{N}$ of primes such that the function $\displaystyle O(z) = \sum_{n \ge 0} a_n z^n$ is meromorphic on $\mathbb{C}$? ...
Qiaochu Yuan's user avatar
9 votes
6 answers
3k views

Primes are pseudorandom?

I've been reading the wonderful slides by Terry Tao and thought about this question. Primes appear to be quite random, and the formal statement should be that there are some characteristics of primes ...
Ilya Nikokoshev's user avatar
9 votes
1 answer
2k views

The large sieve for primes

Let $\Lambda(n)$ be the von Mangoldt function, i.e., $\Lambda(n) = \log p$ for $n$ a prime power $p^k$ and $\Lambda(n) = 0$ for all $n$ that not prime powers. Let $$S(\alpha) = \sum_{n \leq N} \...
H A Helfgott's user avatar
  • 20.2k
16 votes
4 answers
2k views

Arithmetic progressions without small primes

The following question came up in the discussion at How small can a group with an n-dimensional irreducible complex representation be? : Is it known that there are infinitely many primes p for which ...
David E Speyer's user avatar

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