freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-120-square-remainders.english.md

id, challengeType, title, forumTopicId

id	challengeType	title	forumTopicId
5900f3e41000cf542c50fef7	5	Problem 120: Square remainders	301747

Description

Let r be the remainder when (a−1)n + (a+1)n is divided by a2. For example, if a = 7 and n = 3, then r = 42: 63 + 83 = 728 ≡ 42 mod 49. And as n varies, so too will r, but for a = 7 it turns out that rmax = 42. For 3 ≤ a ≤ 1000, find ∑ rmax.

Instructions

Tests

tests:
  - text: <code>euler120()</code> should return 333082500.
    testString: assert.strictEqual(euler120(), 333082500);

Challenge Seed

function euler120() {
  // Good luck!
  return true;
}

euler120();

Solution

// solution required