Questions, not proof records

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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17 source collections · 43 mathematical fields

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Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,28)827W(3, 28) \ge 827 from [AKS14, Table 2].

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

Erdős Problem 331: Ruzsa

Ruzsa suggests that a non-trivial variant of this problem arises if one imposes the stronger condition that A{1,,N}cAN1/2|A \cap \{1,\dots,N\}| \sim c_A N^{1/2} for some constant cA>0c_A>0, and similarly for BB.

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,29)868W(3, 29) \ge 868 from [AKS14, Table 2].

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

Erdős Problem 332

Let ANA\subseteq \mathbb{N} and D(A)D(A) be the set of those numbers which occur infinitely often as a1a2a_1 - a_2 with a1,a2Aa_1, a_2\in A. What conditions on AA are sufficient to ensure D(A)D(A) has bounded gaps?

This is formalised here using the answer(sorry) mechanism. In order to solve this problem one has to provide what the sufficient conditions are, and proof that they imply the desired condition. If the condition is a solution to the problem is up to human judgement.

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,30)903W(3, 30) \ge 903 from [AKS14, Table 2].

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

Erdős Problem 341

Let A={a1<<ak}A=\{a_1 < \cdots < a_k\} be a finite set of integers and extend it to an infinite sequence A={a1<a2<}\overline{A}=\{a_1 < a_2 < \cdots \} by defining an+1a_{n+1} for nkn \geq k to be the least integer exceeding ana_n which is not of the form ai+aja_i + a_j with i,jni,j \leq n. Is it true that the sequence of differences am+1ama_{m+1}-a_m is eventually periodic?

This problem is discussed under Problem 7 on Green's open problems list.

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,31)>930W(3, 31) > 930 from [AKS14, Table 3].

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

Erdős Problem 346

Is it true that for every lacunary, strongly complete sequence A that is not complete whenever infinitely many terms are removed from it, lim A (n + 1) / A n = (1 + √5) / 2?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,32)>1006W(3, 32) > 1006 from [AKS14, Table 3].

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

Erdős Problem 348

For what values of 0m<n0 \leq m < n is there a complete sequence A={a1a2}A = \{a_1 \leq a_2 \leq \cdots\} of integers such that

  1. AA remains complete after removing any mm elements, but
  2. AA is not complete after removing any nn elements.
Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,33)>1063W(3, 33) > 1063 from [AKS14, Table 3].

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

Erdős Problem 349

For what values of t,α(0,)t,\alpha \in (0,\infty) is the sequence tαn\lfloor t\alpha^n\rfloor complete (that is, all sufficiently large integers are the sum of distinct integers of the form tαn\lfloor t\alpha^n\rfloor)?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,34)>1143W(3, 34) > 1143 from [AKS14, Table 3].

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

Erdős Problem 349

It seems likely that the sequence is complete for all for all t>0t>0 and all 1<α<1+521 < \alpha < \frac{1+\sqrt{5}}{2}.

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,35)>1204W(3, 35) > 1204 from [AKS14, Table 3].

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

Erdős Problem 349: Floor 3 Halves Odd

Is it true that the terms of the sequence (3/2)n\lfloor (3/2)^n\rfloor are odd infinitely often and even infinitely often?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,36)>1257W(3, 36) > 1257 from [AKS14, Table 3].

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

Erdős Problem 349: Floor 3 Halves Even

Is it true that the terms of the sequence (3/2)n\lfloor (3/2)^n\rfloor are even infinitely often?

Source checked Jul 26, 20261 pinned Lean statementInspect problem
Source labels openGreen's Open Problems · Combinatorics

Ben Green's Open Problem 14

W(3,37)>1338W(3, 37) > 1338 from [AKS14, Table 3].

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

Erdős Problem 354: I

Let α,βR>0\alpha,\beta\in \mathbb{R}_{>0} such that α/β\alpha/\beta is irrational. Is

\{ \lfloor \beta\rfloor,\lfloor \gamma\beta\rfloor,\lfloor \gamma^2\beta\rfloor,\ldots\}$$ complete?
Source checked Jul 26, 20261 pinned Lean statementInspect problem