MathDB
Positive divisors

Source: Indonesia Mathematics Olympiad 2007 Day 1 Problem 2

June 2, 2008
number theoryrelatively primeDiophantine equationnumber theory proposed

Problem Statement

For every positive integer n n, b(n) b(n) denote the number of positive divisors of n n and p(n) p(n) denote the sum of all positive divisors of n n. For example, b(14)\equal{}4 and p(14)\equal{}24. Let k k be a positive integer greater than 1 1. (a) Prove that there are infinitely many positive integers n n which satisfy b(n)\equal{}k^2\minus{}k\plus{}1. (b) Prove that there are finitely many positive integers n n which satisfy p(n)\equal{}k^2\minus{}k\plus{}1.