Problems / combinatorics
combinatorics / Ramsey theory, arithmetic progressions
Erdos Problem #138: do the van der Waerden numbers grow superexponentially, W(k)^(1/k) -> infinity?
Theorem 1.1: there is an absolute K0 with Wr(k)>kck⌊log2r⌋, c=10−5, for all k≥K0 and r≥2; hence Wr(k)1/k→∞ for each fixed r. Prior work in 2026: Fox-Hunter proved superexponential growth for three colours, and Campos-Fox-Schildkraut proved W2(k)≥(1−o(1))k2k−1, settling W2(k)/2k→∞ but not the limit asked here. Not shown: the companion question W(k+1)−W(k)→∞, or any upper bound improvement.