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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.

1 vote
0 answers
71 views

Is there an upper bound on the number of partitions of a finite set of primes into 3 sets th...

Is there an upper bound on the number of partitions of a finite set $S$ of prime numbers into 3 sets $A$, $B$ and $C$ for which the following holds?: $$ \prod_{p \in A} p \ + \ \prod_{p \in B} p \ = …
39 votes
1 answer
2k views

Prime number races in 2 dimensions

Is the mapping $$f: \ \mathbb{N} \rightarrow \mathbb{Z}[i], \ \ \ n \ \mapsto \sum_{2 < p \leq n \ {\rm prime}} e^{\frac{p-1}{4} \pi i}$$ surjective? In 1999, when I was an undergraduate student, I t …
18 votes
1 answer
649 views

How hard is it to find a prime number with given primitive roots?

Assume that we randomly choose a 100-digit prime number $p$, record which of the first 1000 prime numbers are primitive roots modulo $p$, and then forget about $p$. — How easy or how difficult is it t …
18 votes
2 answers
2k views

Existence of polynomials of degree $\geq 2$ which represent infinitely many prime numbers

To my knowledge it is open so far whether the polynomial $x^2+1 \in \mathbb{Z}[x]$ takes infinitely many prime numbers as values. Is it known so far whether there is at all any polynomial $P \in \math …
3 votes
0 answers
145 views

The bias of consecutive prime numbers towards being incongruent modulo 3

Given a positive integer $n$, let $f_1(n)$ denote the number of pairs of consecutive prime numbers $\leq n$ which are incongruent modulo 3, and let $f_2(n)$ denote the number of pairs of consecutive p …
43 votes
1 answer
1k views

Can't one walk to infinity on the prime numbers with finitely many distinct affine steps?

Let $(a_1,b_1), \dots, (a_k,b_k)$ be finitely many pairs of positive integers, and let $\Gamma$ be the graph whose vertices are the prime numbers and in which two vertices $p$ and $q$ are connected by …
9 votes
2 answers
527 views

Sign of permutation induced by modular exponentiation

Given a prime number $p$ and a primitive root $a$ modulo $p$, let $\sigma_{a,p}$ denote the permutation of the set $\{1, \dots, p-1\}$ which maps $b$ to $a^b$ modulo $p$. Question: Let $p$ be fixed. …
5 votes
0 answers
176 views

Can the integers in an easily computable sequence free of prime numbers always be factored e...

Call a sequence $(a_n)$ of positive integers easily computable if there is a constant $C$ and an algorithm which computes $a_n$ from $n$, $a_1, \dots, a_{n-1}$ and a finite number of integer constant …
2 votes
1 answer
202 views

Endomorphism of the symmetric group of the set of positive integers via action on the prime ...

For a positive integer $n$, let $p_n$ denote the $n$-th prime number. Further let $f: {\rm Sym}(\mathbb{N}) \rightarrow {\rm Sym}(\mathbb{N})$ be the monomorphism which maps a permutation $\sigma$ to …
19 votes
1 answer
2k views

How many primes can there be in a short interval?

Given $n \in \mathbb{N}$, let $\pi(n)$ denote the number of prime numbers $\leq n$. What is $$ \limsup_{m \rightarrow \infty} \left( \limsup_{n \rightarrow \infty} \frac{\pi(n+m) - \pi(n)}{\pi(m)} \ …
2 votes

Reference Request on the existence of $k$ satisfying $P(\Phi_d(2))^k \gt \Phi_d(2)$ for all $d$

Given a positive integer $k$, the natural density of the set of positive integers $n$ whose largest prime factor is smaller than the $k$-th root of $n$ is estimated by the value of the Dickman functio …
Stefan Kohl's user avatar
  • 19.6k
1 vote
Accepted

Set of triple-primes satisfying a certain equation

Yes, there is precisely one such triple of distinct primes with $\alpha \leq 500$, namely $(3, 11, 31)$. It would be a surprising coincidence if there are further such triples for larger $\alpha$.
Stefan Kohl's user avatar
  • 19.6k
10 votes
Accepted

Can $b^4+1$ be a pseudoprime to base 2 (except for Fermat numbers)?

Carl Pomerance conjectured in On the Distribution of Pseudoprimes, Math. Comput. 37, 587-593 (1981) that for large $x$, the number of pseudoprimes $\leq x$ is $$ \frac{x}{e^{(1+o(1))\log{x}\frac{\ …
Stefan Kohl's user avatar
  • 19.6k
38 votes
Accepted

Does the equation $241+2^{2s+1}=m^2$ have a solution?

To answer your first question: there is indeed no $s$ such that $241+2^{2s+1}$ is a perfect square. -- Proof: $2^{2s+1}$ is always congruent to either $2$, $8$ or $32$ modulo $63$, which makes $241+2^ …
Stefan Kohl's user avatar
  • 19.6k
15 votes
Accepted

Lower density of {primes} times themselves

There is no such $m_0$, due to the Erdős–Kac theorem.
Stefan Kohl's user avatar
  • 19.6k

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