Erdős–Selfridge odd covering problem
Erdős–Selfridge odd covering problem
A covering system of the integers is a finite family of congruence classes whose union is all of . The moduli are odd, distinct, and greater than when every is odd, the moduli are pairwise distinct, and for every .
Erdős–Selfridge odd covering problem. Does there exist a covering system of whose moduli are odd, distinct, and greater than ?
The problem is open in both directions and is Erdős's problem #7. An odd covering system would have consequences for the reducibility of trinomials, and the paper gives a kernel-checked exclusion showing that any such covering would have least common multiple exceeding .
Sources & referencesView supporting material
Primary source
Ibrahim Mian and Shayaan Siddique, “Kernel-Checked Exclusions for the Erdős-Selfridge Odd Covering Problem: Any Odd Covering of Z Has lcm Exceeding 10000”, arXiv:2607.25628 (2026).
Additional references
3 papers in this index state this conjecture (2018–2026). The statement above is taken from the most recent of them; the others are arXiv:2507.23041, arXiv:1811.03547.
Progress summary
Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.
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