freeCodeCamp/curriculum/challenges/en/08-coding-interview-prep/project-euler/problem-443-gcd-sequence.en.md

id, challengeType, title

id	challengeType	title
5900f5271000cf542c51003a	5	Problem 443: GCD sequence

Description

Let g(n) be a sequence defined as follows: g(4) = 13, g(n) = g(n-1) + gcd(n, g(n-1)) for n > 4.

The first few values are:

n4567891011121314151617181920...
g(n)1314161718272829303132333451545560...

You are given that g(1 000) = 2524 and g(1 000 000) = 2624152.

Find g(1015).

Instructions

Tests

- text: <code>euler443()</code> should return 2744233049300770.
  testString: 'assert.strictEqual(euler443(), 2744233049300770, ''<code>euler443()</code> should return 2744233049300770.'');'

Challenge Seed

function euler443() {
  // Good luck!
  return true;
}

euler443();

Solution

// solution required