freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-124-ordered-radicals.md

---
id: 5900f3e81000cf542c50fefb
title: 'Problem 124: Ordered radicals'
challengeType: 5
forumTopicId: 301751
dashedName: problem-124-ordered-radicals
---

# --description--

The radical of $n$, $rad(n)$, is the product of the distinct prime factors of $n$. For example, $504 = 2^3 × 3^2 × 7$, so $rad(504) = 2 × 3 × 7 = 42$.

If we calculate $rad(n)$ for $1 ≤ n ≤ 10$, then sort them on $rad(n)$, and sorting on $n$ if the radical values are equal, we get:

<div style="text-align: center;">
  <table cellpadding="2" cellspacing="0" border="0" align="center">
    <tbody>
      <tr>
        <td colspan="2">$Unsorted$</td>
        <td></td>
        <td colspan="3">$Sorted$</td>
      </tr>
      <tr>
        <td>$n$</td>
        <td>$rad(n)$</td>
        <td></td>
        <td>$n$</td>
        <td>$rad(n)$</td>
        <td>$k$</td>
      </tr>
      <tr>
        <td>1</td>
        <td>1</td>
        <td></td>
        <td>1</td>
        <td>1</td>
        <td>1</td>
      </tr>
      <tr>
        <td>2</td>
        <td>2</td>
        <td></td>
        <td>2</td>
        <td>2</td>
        <td>2</td>
      </tr>
      <tr>
        <td>3</td>
        <td>3</td>
        <td></td>
        <td>4</td>
        <td>2</td>
        <td>3</td>
      </tr>
      <tr>
        <td>4</td>
        <td>2</td>
        <td></td>
        <td>8</td>
        <td>2</td>
        <td>4</td>
      </tr>
      <tr>
        <td>5</td>
        <td>5</td>
        <td></td>
        <td>3</td>
        <td>3</td>
        <td>5</td>
      </tr>
      <tr>
        <td>6</td>
        <td>6</td>
        <td></td>
        <td>9</td>
        <td>3</td>
        <td>6</td>
      </tr>
      <tr>
        <td>7</td>
        <td>7</td>
        <td></td>
        <td>5</td>
        <td>5</td>
        <td>7</td>
      </tr>
      <tr>
        <td>8</td>
        <td>2</td>
        <td></td>
        <td>6</td>
        <td>6</td>
        <td>8</td>
      </tr>
      <tr>
        <td>9</td>
        <td>3</td>
        <td></td>
        <td>7</td>
        <td>7</td>
        <td>9</td>
      </tr>
      <tr>
        <td>10</td>
        <td>10</td>
        <td></td>
        <td>10</td>
        <td>10</td>
        <td>10</td>
      </tr>
    </tbody>
  </table>
</div><br>

Let $E(k)$ be the $k$th element in the sorted $n$ column; for example, $E(4) = 8$ and $E(6) = 9$. If $rad(n)$ is sorted for $1 ≤ n ≤ 100000$, find $E(10000)$.

# --hints--

`orderedRadicals()` should return `21417`.

```js
assert.strictEqual(orderedRadicals(), 21417);
```

# --seed--

## --seed-contents--

```js
function orderedRadicals() {

  return true;
}

orderedRadicals();
```

# --solutions--

```js
// solution required
```