Erdős Problem #634: independent continuation
Date: 23 September 2026. Source versions read in full:
634.tex in
gpt_pro_5.4.
1) OBJECTIVE AND NUMBERING
Problem 634 asks which integers occur as the number of congruent triangles tiling a triangle. The supplied file also mentions 633 and 635; those are different problems and are not silently treated as versions of 634. The task here is an arithmetic refinement of the sufficient condition quoted there, not a classification.
2) BALANCING THE FACTORIZATION
Use Zhang's theorem in the form recorded in the official problem discussion: for positive integers $a\ge b$, the number $n^2ab$ is attainable if \[
n\ge3\left\lceil\frac{a^2+b^2+ab-a-b}{ab}\right\rceil.
\] For $m\ge1$, define the explicitly computable sufficient threshold \[
T(m)=3\min_{ab=m,\ a\ge b}\left\lceil\frac ab+\frac ba+1-\frac1a-\frac1b\right\rceil.
\] Then every $mn^2$ with $n\ge T(m)$ is attainable. The source uses only $(a,b)=(m,1)$ and thus obtains $3m$. Taking the minimum is always at least as good, and can be much better. For instance, $m=35=7\cdot5$ gives the expression $97/35$, hence $T(35)\le9$, compared with the source threshold $105$. For $m=143=13\cdot11$, it gives $409/143$, hence $T(143)\le9$, compared with $429$.
3) UNIFORM BOUND FOR BALANCED FACTORS
If $m=ab$ with $1\le a/b\le R$, then \[
T(m)\le3\lceil R+2\rceil,
\] since $b/a\le1$ and the two negative terms can be dropped. Thus the sufficient square multiplier can be bounded independently of $m$ on any family admitting uniformly balanced factors. This follows directly from the quoted theorem; it is not a new tiling construction. More generally, for a proposed count $N$, enumerate every factorization $N=mn^2$ and every $m=ab$. Any one successful inequality certifies attainability. It is unnecessary to restrict to the squarefree decomposition.
4) LIMITATION
Failure of this finite sufficient test proves nothing about nonexistence. In particular it cannot classify small exceptional counts or replace the geometric hypotheses in other tiling theorems. I do not use the source's unrestricted triquadratic equivalence without checking all its geometric side conditions.
7) FINAL
UNRESOLVED. The improvement is an optimized arithmetic certificate for an existing sufficient theorem, not a solution of the classification problem. The theorem was checked against the official record at
https://www.erdosproblems.com/634; no independent proof of Zhang's construction is claimed.
8) COMPLETION ESTIMATE
COMPLETION: 10% This is a subjective estimate of progress toward the entire stated problem, not a probability that the conjecture or an unverified proof is correct.