MathDB

1

Part of 2017 Korea Junior Math Olympiad

Problems(1)

i divides exactly a_i numbers

Source: KJMO 2017 p1

7/26/2019
Find all positive integer nn and nonnegative integer a1,a2,…,ana_1,a_2,\dots,a_n satisfying:
ii divides exactly aia_i numbers among a1,a2,…,ana_1,a_2,\dots,a_n, for each i=1,2,…,ni=1,2,\dots,n. (00 is divisible by all integers.)
number theoryKJMO