MathDB
A problem with series

Source: P5, Mexico Center Regional Olympiad 2019

November 28, 2019
number theory

Problem Statement

A serie of positive integers a1a_{1},a2a_{2},. . . ,ana_{n} is autodelimitedauto-delimited if for every index ii that holds 1in1\leq i\leq n, there exist at least aia_{i} terms of the serie such that they are all less or equal to ii. Find the maximum value of the sum a1+a2++ana_{1}+a_{2}+\cdot \cdot \cdot+a_{n}, where a1a_{1},a2a_{2},. . . ,ana_{n} is an autodelimitedauto-delimited serie.