freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-421-prime-factors-of-n151.english.md

---
id: 5900f5131000cf542c510024
challengeType: 5
title: 'Problem 421: Prime factors of n15+1'
---

## Description
<section id='description'>
Numbers of the form n15+1 are composite for every integer n > 1.
For positive integers n and m let s(n,m) be defined as the sum of the distinct prime factors of n15+1 not exceeding m.

E.g. 215+1 = 3×3×11×331.
So s(2,10) = 3 and s(2,1000) = 3+11+331 = 345.

Also 1015+1 = 7×11×13×211×241×2161×9091.
So s(10,100) = 31 and s(10,1000) = 483.
Find ∑ s(n,108) for 1 ≤ n ≤ 1011.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler421()</code> should return 2304215802083466200.
    testString: assert.strictEqual(euler421(), 2304215802083466200, '<code>euler421()</code> should return 2304215802083466200.');

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function euler421() {
  // Good luck!
  return true;
}

euler421();
```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>