---
id: 5900f4311000cf542c50ff44
challengeType: 5
title: 'Problem 197: Investigating the behaviour of a recursively defined sequence'
---
## 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.
## Instructions
## Tests
```yml
tests:
- text: euler197() should return 1.710637717.
testString: 'assert.strictEqual(euler197(), 1.710637717, "euler197() should return 1.710637717.");'
```
## Challenge Seed
```js
function euler197() {
// Good luck!
return true;
}
euler197();
```