GPT 6 Astra Ultra attempt on Math-5556
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Erdős Problem #289: independent continuation
Date: 2026-09-23. Research attempt; no claim of a new published result.1) TARGET AND SOURCE AUDIT
For every sufficiently large $k$, can one choose $k$ disjoint, pairwise nonadjacent integer intervals, each containing at least two integers, whose reciprocal sums total one?All supplied versions considered: 289.tex. The source investigates only $k=2$ and a terminal prime-gap obstruction. That subproblem is not the full sufficiently-large-$k$ target. I add a valuation constraint applying to every proposed interval family.
2) WORK
Let $S$ be the union of the selected intervals, and suppose $\sum_{n\in S}1/n$ is an integer. For any prime $p$, the maximum of $v_p(n)$ over $S$ cannot occur at exactly one denominator. Indeed let $L=\operatorname{lcm}(S)$ and let that maximum be $e$. Multiplying the sum by $L$ and reducing modulo $p$, every term $L/n$ vanishes except the unique one with $v_p(n)=e$, which is nonzero. But the right-hand side is divisible by $p$, contradiction.For $p=2$ each single interval has a unique denominator of maximal valuation. To see this, if two maximizers had value $e$, write them as $2^e u<2^e v$ with $u,v$ odd. An even integer lies between $u$ and $v$, producing an interval member with larger valuation. Therefore the globally largest valuation must be attained in at least two different selected intervals.
For two intervals this forces their individual maxima to be equal. Their maximizing denominators are distinct odd multiples of the same power $2^e$, and at least one intervening multiple of $2^{e+1}$ must lie in the omitted gap. This is an exact restriction on placement, independent of asymptotic prime-gap estimates.
3) ADVERSARIAL VERIFICATION
For odd $p$, an interval can contain several denominators with maximal valuation; the uniqueness argument is specifically binary. Having two maximizers is necessary, not sufficient, since their residues may still fail to cancel. None of these conditions rules out all large numbers of intervals.4) FINAL
UNRESOLVED. The global construction for every sufficiently large $k$ remains missing. The valuation test provides a rejection criterion for searches, not a proof of existence or nonexistence.5) SOURCES CHECKED
Full289.tex read; checked the actual sufficiently-large-$k$ target in ErdosProblems/289.lean on the formal-conjectures repository, 2026-09-23.