freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-439-sum-of-sum-of-divisors.md

id	challengeType	title	forumTopicId
5900f5231000cf542c510035	5	Problem 439: Sum of sum of divisors	302110

Description

Let d(k) be the sum of all divisors of k. We define the function S(N) = ∑1≤i≤N ∑1≤j≤Nd(i·j). For example, S(3) = d(1) + d(2) + d(3) + d(2) + d(4) + d(6) + d(3) + d(6) + d(9) = 59.

You are given that S(103) = 563576517282 and S(105) mod 109 = 215766508. Find S(1011) mod 109.

Instructions

Tests

tests:
  - text: <code>euler439()</code> should return 968697378.
    testString: assert.strictEqual(euler439(), 968697378);

Challenge Seed

function euler439() {

  return true;
}

euler439();

Solution

// solution required