Odd and Even Solutions

Problem

Consider the equation

E: x1+2x2+3x3+⋯+nxn=2017.E:\ x_1 + 2x_2 + 3x_3 + \cdots + nx_n = 2017.

1. Find the largest nn for which EE has a solution in positive integers x1,…,xnx_1, \dots, x_n. 2. Call a positive-integer solution of EE odd if nn is odd and even if nn is even. Prove that the total number of odd solutions equals the total number of even solutions.

Answer

Solution

Difficulty9/10
Topicscombinatorics, number theory, Counting, Estimation, Casework

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