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Erdős Problem #671

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erdos-671Analysisposed by Paul Erdős, 1982recorded: candidate

1 attempt · 1 machine check · no person has looked

Statement

For triangular arrays of nodes ain[1,1]a_i^n\in[-1,1] let Lnf\mathcal{L}^nf be the Lagrange interpolation polynomials of a continuous ff, with fundamental polynomials pinp_i^n. Is there a choice of nodes such that for every continuous ff there is some xx where lim supnipin(x)=\limsup_n \sum_i\lvert p_{i}^n(x)\rvert=\infty and yet Lnf(x)f(x)\mathcal{L}^nf(x) \to f(x)? Is there a choice with lim supnipin(x)=\limsup_n \sum_i\lvert p_{i}^n(x)\rvert=\infty for every xx, yet for every continuous ff some xx has Lnf(x)f(x)\mathcal{L}^nf(x)\to f(x)? Both questions are claimed resolved in the affirmative.

Context

Both parts claimed answered affirmatively, with a Lean formalization; two proof claims are filed on erdosproblems.com but the problem is still listed open

A numbered Erdos problem that carries a $250 Erdos prize, setting it above the typical entry in the catalog.

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Attempts

1 attempt

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  • #1

    Attempt 1

    constructionGPT-5.5 Pro, Codex with Liam Price ·
    AI involvement
    ai discovered
    the result was found by a model.
    models
    GPT-5.5 Pro, Codex
    people
    Liam Price

    GPT Pro produced the affirmative resolutions of both questions and Codex the Lean formalization; the humans directed the models with a writing-style prompt and cleaned up terminology, a workflow the site's owner singled out as unusually readable for AI-assisted papers.

    Both parts claimed answered affirmatively, with a Lean formalization; two proof claims are filed on erdosproblems.com but the problem is still listed open

    Reviews

    0 human reviews · 1 machine check

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    • Machine check · not human verification

      machine: correct

      Recorded from Lean ·

      scope Lean formalization of the result

      The argument comes with a Codex-produced Lean formalization checkable online; no independent audit of statement fidelity, and erdosproblems.com still lists the problem open with the claims filed.

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Discussion

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