ASU 459 All Soviet Union MO 1987 T_0 set consists of all (2k)!
Source:
August 7, 2019
setnumber theorycombinatorics
Problem Statement
The set consists of all the numbers, representable as . The set is obtained from by adding all the finite sums of different numbers, that belong to . Prove that there is a natural number, that doesn't belong to .