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Erdős-Mahler Conjecture


The Erdős-Mahler conjecture asserts that an irrational number is a Liouville number if infinitely many of its regular continued fraction convergents p_n/q_n have P(p_nq_n) bounded by a fixed constant, where P(m) is the largest prime factor of |m| for a nonzero integer m, with P(1)=P(-1)=1 (Erdős and Mahler 1939, Marques 2026). The condition restricts the prime factors of both the numerator and the denominator along the same infinite subsequence.

Marques (2026) reports that, for every finite real number tau>=4, there is a Cantor set K_tau subset (1,2) such that every xi in K_tau has irrationality measure tau and infinitely many regular continued fraction convergents of the form 2^a/3^b, with a and b positive integers. The claimed construction would refute the conjecture, since finite irrationality measure excludes Liouville numbers.


See also

Continued Fraction, Irrationality Measure, Liouville Number

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References

Erdős, P. and Mahler, K. "Some Arithmetical Properties of the Convergents of a Continued Fraction." J. London Math. Soc. 14, 12-18, 1939. https://doi.org/10.1112/jlms/s1-14.1.12.Marques, D. "A Counterexample to the Erdős-Mahler Conjecture." 10 Nov 2026. https://arxiv.org/abs/2611.13604v1.

Cite this as:

Weisstein, Eric W. "Erdős-Mahler Conjecture." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Erdos-MahlerConjecture.html

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