MathDB
Existence of a 100 disks

Source: Czech-Polish-Slovak Match 2019 P5

July 15, 2019
combinatorics

Problem Statement

Determine whether there exist 100100 disks D2,D3,,D101D_2,D_3,\ldots ,D_{101} in the plane such that the following conditions hold for all pairs (a,b)(a,b) of indices satisfying 2a<b1012\le a< b\le 101:
[*] If aba|b then DaD_a is contained in DbD_b. [*] If gcd(a,b)=1\gcd (a,b)=1 then DaD_a and DbD_b are disjoint.
(A disk D(O,r)D(O,r) is a set of points in the plane whose distance to a given point OO is at most a given positive real number rr.)