MathDB
Sequence of integers

Source: 2019 Second Round - Poland

July 8, 2019
algebracombinatorics

Problem Statement

Let b0,b1,b2,b_0, b_1, b_2, \ldots be a sequence of pairwise distinct nonnegative integers such that b0=0b_0=0 and bn<2nb_n<2n for all positive integers nn. Prove that for each nonnegative integer mm there exist nonnegative integers k,k, \ell such that \begin{align*} b_k+b_{\ell}=m. \end{align*}