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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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Claim. Let n<m<c\mathfrak n<\mathfrak m<\mathfrak c be cardinals. A family of analytic functions taking at most n\mathfrak n distinct values at every point has at most n\mathfrak n members. This is the remark after the theorem in P. Erdős, An interpolation problem associated with the continuum hypothesis, Michigan Math. J. 11 (1964), 9--10 (p. 10), proved by the theorem's counting argument. Two distinct entire functions agree on a countable set, so in a subfamily of n+≤m\mathfrak n^+\le\mathfrak m functions fewer than c\mathfrak c points carry a coincidence, and at any other point the subfamily takes n+\mathfrak n^+ distinct values. For Problem 1119, with the problem's m\mathfrak m in the role of n\mathfrak n, the answer is yes in ZFC for every m>ℵ0\mathfrak m>\aleph_0 with m+<c\mathfrak m^+<\mathfrak c.

Covers. Every cardinal m\mathfrak m of the problem with m+<c\mathfrak m^+<\mathfrak c. The remaining case m+=c\mathfrak m^+=\mathfrak c is undecidable by Kumar and Shelah's model and Schilhan and Weinert's result. Hayman's 1974 list calls the case m+<c\mathfrak m^+<\mathfrak c easy to see, which is how the site's commentary records it.

Depends on. No page of this wiki.

Acceptance. Refereed: the result appears in a journal paper in the Michigan Mathematical Journal.

Formalization. The formalization link is Boris Alexeev's lean-proofs file src/latest/ErdosProblems/Erdos1119.lean, at the revision that formal-conjectures names as the formal proof of erdos_1119.variants.easy_case. Its header calls it a formalization of a solution to the problem and names Paul Erdős as the informal author and Codex and GPT-5.6 Sol as the formal authors. It proves erdos_1119.variants.easy_case and Erdős's countable theorem. The corpus has not built it, so no formalized evidence is listed. A separate Lean package by Collin Yuanjie Ren, noted in the community database, formalizes Erdős's countable-values theorem in both directions. The problem asks only about m>ℵ0\mathfrak m>\aleph_0, so that package is not a claim about it.