IMO 1982 LL CAN15
Show that the set S of natural numbers n for which 3/n
IMO 1982 LL CAN15
Origin: CAN
Problem
Show that the set S of natural numbers n for which 3/n cannot be written as the sum of two reciprocals of natural numbers (S = {n | 3/n ̸= 1/p + 1/q for any p, q \inN}) is not the union of finitely many arithmetic progressions.