---
id: 5900f41a1000cf542c50ff2c
challengeType: 5
title: 'Problem 173: Using up to one million tiles how many different "hollow" square laminae can be formed?'
forumTopicId: 301808
---
## Description
We shall define a square lamina to be a square outline with a square "hole" so that the shape possesses vertical and horizontal symmetry. For example, using exactly thirty-two square tiles we can form two different square laminae:
With one-hundred tiles, and not necessarily using all of the tiles at one time, it is possible to form forty-one different square laminae.
Using up to one million tiles how many different square laminae can be formed?
## Instructions
## Tests
```yml
tests:
- text: euler173() should return 1572729.
testString: assert.strictEqual(euler173(), 1572729);
```
## Challenge Seed
```js
function euler173() {
// Good luck!
return true;
}
euler173();
```