MathDB
Strictly decreasing sequences

Source:

September 9, 2010
algebraSequencePartial OrdersDivisibilityIMO Shortlistcombinatorics

Problem Statement

Consider the set of all strictly decreasing sequences of nn natural numbers having the property that in each sequence no term divides any other term of the sequence. Let A=(aj)A = (a_j) and B=(bj)B = (b_j) be any two such sequences. We say that AA precedes BB if for some kk, ak<bka_k < b_k and ai=bia_i = b_i for i<ki < k. Find the terms of the first sequence of the set under this ordering.