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Erdős-Graham Binomial Divisor Problem


The Erdős-Graham binomial divisor problem asks whether there is a positive constant c such that every binomial coefficient (n; k) with 1<=k<n has a divisor d satisfying cn<d<=n (Erdős and Graham 1976). Since (n; k)=(n; n-k), it is enough to consider 1<=k<=n/2.

Bui et al. (2026) refuted the conjecture in general while proving a strong positive result when k is sufficiently large. For every sufficiently small epsilon>0 and all sufficiently large n, if

 exp((lnn)^(2/3+epsilon))<=k<=n/2,

then (n; k) has a divisor in the interval (n-n/(lnn)^(1/4),n]. In the other direction, for every sufficiently large fixed k_0 and sufficiently small delta>0, there are infinitely many ordered pairs (n,k) with

 k_0<k<=delta(lnlnn)^(1/2)

for which (n; k) has no divisor in the interval (241nlnlnk/lnk,n]. The latter result rules out a universal positive constant c.

The main ideas in the proof of an intermediate covering theorem were developed by the authors in interactive sessions with ChatGPT 5.5 Pro (Bui et al. 2026).


See also

Binomial Coefficient, Divisor, Erdős Problems

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References

Bui, H. M.; Naprienko, S.; Pratt, K.; and Zaharescu, A. "Binomial Coefficients with Divisors Avoiding an Interval." 30 Jun 2026. https://arxiv.org/abs/2605.21221.Erdős, P. and Graham, R. L. "On the Prime Factors of (n; k)." Fibonacci Quart. 14, 348-352, 1976.

Cite this as:

Weisstein, Eric W. "Erdős-Graham Binomial Divisor Problem." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Erdos-GrahamBinomialDivisorProblem.html

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