id	title	challengeType	forumTopicId	dashedName
5900f5041000cf542c510016	Problem 407: Idempotents	5	302075	problem-407-idempotents

--description--

mirror of https://github.com/freeCodeCamp/freeCodeCamp.git

If we calculate a2 mod 6 for 0 ≤ a ≤ 5 we get: 0,1,4,3,4,1.

The largest value of a such that a2 ≡ a mod 6 is 4. Let's call M(n) the largest value of a < n such that a2 ≡ a (mod n). So M(6) = 4.

Find ∑M(n) for 1 ≤ n ≤ 107.

--hints--

euler407() should return 39782849136421.

assert.strictEqual(euler407(), 39782849136421);

function euler407() {

  return true;
}

euler407();

// solution required