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Pyramid with largest absolute value

Source: Ukrainian Mathematical Olympiad 2024. Day 1, Problem 8.2

March 19, 2024
combinatoricsconstructionabsolute value

Problem Statement

There is a table with n>2n > 2 cells in the first row, n1n-1 cells in the second row is a cell, n2n-2 in the third row, \ldots, 11 cell in the nn-th row. The cells are arranged as shown below.
https://i.ibb.co/0Z1CR0c/UMO24-8-2.png
In each cell of the top row Petryk writes a number from 11 to nn, so that each number is written exactly once. For each other cell, if the cells directly above it contains numbers a,ba, b, it contains number ab|a-b|. What is the largest number that can be written in a single cell of the bottom row?
Proposed by Bogdan Rublov