MathDB
triangle of numbers, under any two consecutive numbers their sum is written

Source: Mexican Mathematical Olympiad 2000 OMM P2

July 28, 2018
number theoryPascal's Triangle

Problem Statement

A triangle of numbers is constructed as follows. The first row consists of the numbers from 11 to 20002000 in increasing order, and under any two consecutive numbers their sum is written. (See the example corresponding to 55 instead of 20002000 below.) What is the number in the lowermost row?
1 2 3 4 5 3 5 7 9 8 12 16 20 28 4