We improve known bounds for the maximum number of pairwise disjoint arithmetic progressions using distinct moduli less than x. We close the gap between upper and lower bounds even further under the assumption of a conjecture from combinatorics about Δ-systems (also known as sunflowers).
Institut de Mathématiques de Jussieu, UMR 7586, Université Paris Diderot - Paris 7, UFR de Mathématiques, case 7012, Bâtiment Chevaleret, 75205 Paris Cedex 13, France