freeCodeCamp/curriculum/challenges/chinese/10-coding-interview-prep/project-euler/problem-197-investigating-the-behaviour-of-a-recursively-defined-sequence.md

---
id: 5900f4311000cf542c50ff44
challengeType: 5
videoUrl: ''
title: 问题197：研究递归定义的序列的行为
---

## Description
<section id="description">给定函数f（x）=⌊230.403243784-x2⌋×10-9（⌊⌊是floor函数），序列un由u0 = -1和un + 1 = f（un）定义。 <p>找到n + 1012的un + un + 1.在小数点后面给出9位数的答案。 </p></section>

## Instructions
<section id="instructions">
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler197()</code>应该返回1.710637717。
    testString: assert.strictEqual(euler197(), 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>