ASU 307 All Soviet Union MO 1981 4 rows in a rectangular table
Source:
July 23, 2019
combinatoricscombinatorial geometry
Problem Statement
The rectangular table has four rows. The first one contains arbitrary natural numbers (some of them may be equal). The consecutive lines are filled according to the rule: we look through the previous row from left to the certain number and write the number if was met times. Prove that the second row coincides with the fourth one.