MathDB
Pairwise gcd is equal to gcd of all elements

Source: China TSTST 3 Day 2 Problem 2

March 18, 2017
greatest common divisornumber theory

Problem Statement

Show that there exists a positive real CC such that for any naturals H,NH,N satisfying H3,NeCHH \geq 3, N \geq e^{CH}, for any subset of {1,2,,N}\{1,2,\ldots,N\} with size CHNlnN\lceil \frac{CHN}{\ln N} \rceil, one can find HH naturals in it such that the greatest common divisor of any two elements is the greatest common divisor of all HH elements.