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2412.05077

On Convergents of Proper Continued Fractions

Niels Langeveld, David Ralston

correctmedium confidence
Category
math.DS
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper’s Theorem 3.11 states exactly the sought equivalence for even candidates: p = p2, q = q2 occurs iff there exists a divisor a | p with Tp(x) + Ta(x) > 1; it proves this via a Beatty-sequence characterization and the identity q = ⌊p/x⌋ + 1 for even candidates . The candidate model independently proves the same equivalence by an explicit tail-parameterization t of the PCF, deriving formulas for T_{p2}(x) and T_{a1}(x) that force T_{p2}(x) + T_{a1}(x) > 1 in one direction and construct digits from a|p with t = (1−Tp)/Ta in the other. The two arguments are correct and substantively different in method: the paper uses Beatty sequences, while the model uses explicit algebra on the first two digits and tail. Key identities p2 = a1 b2 and q2 = b1 b2 + a2 used in both align with equation (10) in the paper , and the uniqueness of the even candidate denominator q = ⌊p/x⌋ + 1 matches Lemma 3.3 . The fractional-part map notation TN(x) = {N/x} is consistent across both .

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The main classification result for even second convergents (Theorem 3.11) is correct and neatly characterized by a simple inequality involving fractional parts. The argument is clear and leverages a Beatty-sequence viewpoint that complements the odd-index case. The exposition could benefit from a brief algebraic alternative (as in the model’s tail-parameter derivation) to illuminate the inequality, but the current proof is sound. Overall presentation and context are strong; only minor clarity improvements are suggested.