---
id: 5900f5181000cf542c51002a
challengeType: 5
title: 'Problem 427: n-sequences'
---
## Description
A sequence of integers S = {si} is called an n-sequence if it has n elements and each element si satisfies 1 ≤ si ≤ n. Thus there are nn distinct n-sequences in total.
For example, the sequence S = {1, 5, 5, 10, 7, 7, 7, 2, 3, 7} is a 10-sequence.
For any sequence S, let L(S) be the length of the longest contiguous subsequence of S with the same value.
For example, for the given sequence S above, L(S) = 3, because of the three consecutive 7's.
Let f(n) = ∑ L(S) for all n-sequences S.
For example, f(3) = 45, f(7) = 1403689 and f(11) = 481496895121.
Find f(7 500 000) mod 1 000 000 009.
## Instructions
## Tests
```yml
tests:
- text: euler427() should return 97138867.
testString: 'assert.strictEqual(euler427(), 97138867, "euler427() should return 97138867.");'
```
## Challenge Seed
```js
function euler427() {
// Good luck!
return true;
}
euler427();
```