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Open-problem statements, with their sources attached.

Each statement record keeps the mathematical question, a dated status source, accessible references, and any pinned Lean formulation separate from proof verification.

“Open” is a dated source assertion. In these pinned sources, sorry marks an admitted statement, not a proof. Source indexing does not mean the formulation has been independently built or certified by Therefore.
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1194 of 1194 statement records

17 source collections · 43 mathematical fields

Source labels openErdős Problems · Number theory

Erdős Problem 421

Is there a sequence 1d1<d2<1 \le d_1 < d_2 < \dots with density 1 such that all products uivdi\prod_{u \le i \le v} d_i are distinct?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 422

Does f(n)f(n) miss infinitely many integers?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 422: Surjective

Is ff surjective?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 422: Growth Rate

How does ff grow?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 422: Eventually Const

Does ff become stationary at some point?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 424

Let a1=2a_1 = 2 and a2=3a_2 = 3 and continue the sequence by appending to a1,,ana_1, \ldots, a_n all possible values of aiaj1a_i a_j - 1 with iji \neq j. Is it true that the set of integers which eventually appear has positive density?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 428

Is there a set ANA\subseteq \mathbb{N} such that, for infinitely many nn, all of nan-a are prime for all aAa\in A with 0<a<n0 < a < n and lim infA[1,x]π(x)>0?\liminf\frac{\lvert A\cap [1,x]\rvert}{\pi(x)}>0?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 445

Is it true that, for any c>1/2c>1/2, if pp is a sufficiently large prime then, for any n0n\geq 0, there exist a,b(n,n+pc)a,b\in(n,n+p^c) such that ab1(modp)ab\equiv 1\pmod{p}?

This is discussed in this MathOverflow question [MathOverflow].

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 454

Is it true that limsup (fun n => (f n - 2 * n.nth Prime : ℕ∞)) atTop = ⊤?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openOther · Combinatorics

Beaver Math Olympiad (BMO)

BMO#1

Let (an)n1(a_n)_{n \ge 1} and (bn)n1(b_n)_{n \ge 1} be two sequences such that (a1,b1)=(1,2)(a_1, b_1) = (1, 2) and

(a_n-b_n, 4b_n+2) & \text{if }a_n \ge b_n \\ (2a_n+1, b_n-a_n) & \text{if }a_n < b_n \end{cases}$$ for all positive integers $n$. Does there exist a positive integer $i$ such that $a_i = b_i$? The first 10 values of $(a_n, b_n)$ are $(1, 2), (3, 1), (2, 6), (5, 4), (1, 18), (3, 17), (7, 14), (15, 7), (8, 30), (17, 22)$. [BMO#1](https://wiki.bbchallenge.org/wiki/Beaver_Math_Olympiad#1._1RB1RE_1LC0RA_0RD1LB_---1RC_1LF1RE_0LB0LE_(bbch)) is equivalent to asking whether the 6-state Turing machine [`1RB1RE_1LC0RA_0RD1LB_---1RC_1LF1RE_0LB0LE`](https://wiki.bbchallenge.org/wiki/1RB1RE_1LC0RA_0RD1LB_---1RC_1LF1RE_0LB0LE) halts or not. There is presently no consensus on whether the machine halts or not, hence the problem is formulated using `answer(sorry) ↔`. The machine was discovered by [bbchallenge.org](bbchallenge.org) contributor Jason Yuen on June 25th 2024.
Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openErdős Problems · Number theory

Erdős Problem 455

Let q : ℕ → ℕ be a strictly increasing sequence of primes such that q (n + 2) - q (n + 1) ≥ q (n + 1) - q n. Must lim q n / (n ^ 2) = ∞?

Source checked Jul 26, 20261 pinned Lean statementInspect problem