freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-136-singleton-difference.english.md

---
id: 5900f3f51000cf542c50ff07
challengeType: 5
title: 'Problem 136: Singleton difference'
---

## Description
<section id='description'>
The positive integers, x, y, and z, are consecutive terms of an arithmetic progression. Given that n is a positive integer, the equation, x2 − y2 − z2 = n, has exactly one solution when n = 20:
132 − 102 − 72 = 20
In fact there are twenty-five values of n below one hundred for which the equation has a unique solution.
How many values of n less than fifty million have exactly one solution?
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler136()</code> should return 2544559.
    testString: 'assert.strictEqual(euler136(), 2544559, "<code>euler136()</code> should return 2544559.");'

```

</section>

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

<div id='js-seed'>

```js
function euler136() {
  // Good luck!
  return true;
}

euler136();
```

</div>



</section>

## Solution
<section id='solution'>

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