Erdős problem 70
Erdős Problem 70: Let be the cardinality of the continuum, let be a countable ordinal, and let . Is it true that ?
Sources
FormalConjectures/ErdosProblems/
70.lean
Retained formal statement
**The relation at **: for finite , where is the first uncountable ordinal.
Note that is *not* a countable ordinal, so this is not directly an instance of the main Erdős problem (which asks for *countable* ). Under CH, , making this a self-referential question about .
True ↔ ∀ (n : ℕ), 2 ≤ n → Erdos70.OrdinalCardinalRamsey3 Cardinal.continuum.ord (Cardinal.aleph 1).ord ↑nOpenStatement only, no proof