freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-36-double-base-palindromes.english.md

---
id: 5900f3901000cf542c50fea3
challengeType: 5
title: 'Problem 36: Double-base palindromes'
---

## Description
<section id='description'>
The decimal number, 585 = 10010010012 (binary), is palindromic in both bases.
Find the sum of all numbers, less than n, whereas 1000 <= n <= 1000000, which are palindromic in base 10 and base 2.
(Please note that the palindromic number, in either base, may not include leading zeros.)
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>doubleBasePalindromes(1000)</code> should return 1772.
    testString: assert(doubleBasePalindromes(1000) == 1772, '<code>doubleBasePalindromes(1000)</code> should return 1772.');
  - text: <code>doubleBasePalindromes(50000)</code> should return 105795.
    testString: assert(doubleBasePalindromes(50000) == 105795, '<code>doubleBasePalindromes(50000)</code> should return 105795.');
  - text: <code>doubleBasePalindromes(500000)</code> should return 286602.
    testString: assert(doubleBasePalindromes(500000) == 286602, '<code>doubleBasePalindromes(500000)</code> should return 286602.');
  - text: <code>doubleBasePalindromes(1000000)</code> should return 872187.
    testString: assert(doubleBasePalindromes(1000000) == 872187, '<code>doubleBasePalindromes(1000000)</code> should return 872187.');

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function doubleBasePalindromes(n) {
  // Good luck!
  return n;
}

doubleBasePalindromes(1000000);
```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>