freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-197-investigating-the-behaviour-of-a-recursively-defined-sequence.english.md

---
id: 5900f4311000cf542c50ff44
challengeType: 5
title: 'Problem 197: Investigating the behaviour of a recursively defined sequence'
---

## Description
<section id='description'>
Given is the function f(x) = ⌊230.403243784-x2⌋ × 10-9 ( ⌊ ⌋ is the floor-function),
the sequence un is defined by u0 = -1 and un+1 = f(un).

Find un + un+1 for n = 1012.
Give your answer with 9 digits after the decimal point.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler197()</code> should return 1.710637717.
    testString: assert.strictEqual(euler197(), 1.710637717, '<code>euler197()</code> should return 1.710637717.');

```

</section>

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

<div id='js-seed'>

```js
function euler197() {
  // Good luck!
  return true;
}

euler197();
```

</div>



</section>

## Solution
<section id='solution'>

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