freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-258-a-lagged-fibonacci-sequence.md

---
id: 5900f46e1000cf542c50ff81
title: 'Problem 258: A lagged Fibonacci sequence'
challengeType: 5
forumTopicId: 301906
dashedName: problem-258-a-lagged-fibonacci-sequence
---

# --description--

A sequence is defined as:

gk = 1, for 0 ≤ k ≤ 1999 gk = gk-2000 + gk-1999, for k ≥ 2000. Find gk mod 20092010 for k = 1018.

# --hints--

`euler258()` should return 12747994.

```js
assert.strictEqual(euler258(), 12747994);
```

# --seed--

## --seed-contents--

```js
function euler258() {

  return true;
}

euler258();
```

# --solutions--

```js
// solution required
```
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00			`---`
			`id: 5900f46e1000cf542c50ff81`
			`title: 'Problem 258: A lagged Fibonacci sequence'`
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`challengeType: 5`
fix(curriculum): Added forumTopicId to remaining 1200 challeng… (#36558) 2019-08-05 09:17:33 -07:00			`forumTopicId: 301906`
feat(curriculum): restore seed + solution to Chinese (#40683) * feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com> 2021-01-13 03:31:00 +01:00			`dashedName: problem-258-a-lagged-fibonacci-sequence`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00			`---`

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`# --description--`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`A sequence is defined as:`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`gk = 1, for 0 ≤ k ≤ 1999 gk = gk-2000 + gk-1999, for k ≥ 2000. Find gk mod 20092010 for k = 1018.`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`# --hints--`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`euler258()` should return 12747994.
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			```js
			`assert.strictEqual(euler258(), 12747994);`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00			```

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`# --seed--`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`## --seed-contents--`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
			```js
			`function euler258() {`
fix: remove Good luck! comment from challenge seed code (#39575) 2020-09-15 09:57:40 -07:00
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00			`return true;`
			`}`

			`euler258();`
			```

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`# --solutions--`
feat(challenge-md): Add initial markdown challenge files 2018-09-30 23:01:58 +01:00
			```js
			`// solution required`
			```