---
id: 5900f4ed1000cf542c50ffff
challengeType: 5
title: 'Problem 383: Divisibility comparison between factorials'
forumTopicId: 302047
---
## Description
Let f5(n) be the largest integer x for which 5x divides n.
For example, f5(625000) = 7.
Let T5(n) be the number of integers i which satisfy f5((2·i-1)!) < 2·f5(i!) and 1 ≤ i ≤ n.
It can be verified that T5(103) = 68 and T5(109) = 2408210.
Find T5(1018).
## Instructions
## Tests
```yml
tests:
- text: euler383() should return 22173624649806.
testString: assert.strictEqual(euler383(), 22173624649806);
```
## Challenge Seed
```js
function euler383() {
// Good luck!
return true;
}
euler383();
```