---
id: 5900f4291000cf542c50ff3b
challengeType: 5
title: 'Problem 188: The hyperexponentiation of a number'
---
## Description
The hyperexponentiation or tetration of a number a by a positive integer b, denoted by a↑↑b or ba, is recursively defined by:
a↑↑1 = a,
a↑↑(k+1) = a(a↑↑k).
Thus we have e.g. 3↑↑2 = 33 = 27, hence 3↑↑3 = 327 = 7625597484987 and 3↑↑4 is roughly 103.6383346400240996*10^12.
Find the last 8 digits of 1777↑↑1855.
## Instructions
## Tests
```yml
tests:
- text: euler188() should return 95962097.
testString: assert.strictEqual(euler188(), 95962097, 'euler188() should return 95962097.');
```
## Challenge Seed
```js
function euler188() {
// Good luck!
return true;
}
euler188();
```