Erdős Problem a Daythe open tracker

Erdős Problem #70

OPENdatabase updated 2025-08-31

No proof or disproof is known, and it isn't known whether a finite computation could settle it.

What the community database records, not our verdict. erdosproblems.com no longer shows statuses (why).

`OrdinalCardinalRamsey3 α β c` asserts the 3-uniform ordinal Ramsey property \(\alpha \to (\beta, c)^3_2\). It states that for any 2-coloring of all 3-element subsets of (the ordinal type) \(\alpha\), one of the following must hold: * There is a red-monochromatic subset of order type \(\beta\): every 3-element sub-subset is colored red. (Formally: a set \(s \subseteq \alpha\) with \(\operatorname{typeLT} s = \beta\) such that any three distinct elements of \(s\) are colored red.) * There is a blue-monochrom

`RealCardinalRamsey3 β c` asserts the 3-uniform partition relation \(\mathfrak{c} \to (\beta, c)^3_2\), where \(\mathfrak{c}\) is the order type of the real numbers with their usual order. It states that for any 2-coloring of all 3-element subsets of \(\mathbb{R}\), one of the following must hold: * There is a red-monochromatic subset of order type \(\beta\): the range of an order embedding `β.ToType ↪o ℝ` such that any three distinct elements of the range are colored red. * There is a blue-monochromati

**Erdős Problem 70**: Let \(\mathfrak{c}\) be the order type of the real numbers, let \(\beta\) be a countable ordinal, and let \(2 \le n < \omega\). Is it true that \(\mathfrak{c} \to (\beta, n)^3_2\)? Note: The cases \(n \le 3\) are trivially true (compare `omega_three`), so the genuine content of the conjecture begins at \(n = 4\).
Statement as formalized in Formal Conjectures (Google DeepMind, Apache-2.0) · their label: research open · 4 further variants / known partial results in the Lean file. The authoritative wording is on erdosproblems.com/70.
Prizenone
Topicsgraph theory, ramsey theory, set theory
Statement in LeanFormal Conjectures
Solution in Leanno
Original pageerdosproblems.com/70
WORKING REPORT BY THIS SITE · JUL 26, 2026

Read our working report →

live page is OPEN with no worker/claim; verified \(n\leq3\) for all countable \(\beta\) and, modulo Jones 2018, every finite \(n\) for \(\beta\leq\omega\cdot2+1\), leaving \(n\geq4,\ \beta\geq\omega\c

PARTIAL