2018-09-30 22:01:58 +00:00
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---
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id: 5900f3e41000cf542c50fef7
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challengeType: 5
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title: 'Problem 120: Square remainders'
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---
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## Description
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<section id='description'>
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Let r be the remainder when (a−1)n + (a+1)n is divided by a2.
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For example, if a = 7 and n = 3, then r = 42: 63 + 83 = 728 ≡ 42 mod 49. And as n varies, so too will r, but for a = 7 it turns out that rmax = 42.
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For 3 ≤ a ≤ 1000, find ∑ rmax.
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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2018-10-04 13:37:37 +00:00
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tests:
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- text: <code>euler120()</code> should return 333082500.
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2018-10-20 18:02:47 +00:00
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testString: assert.strictEqual(euler120(), 333082500, '<code>euler120()</code> should return 333082500.');
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2018-09-30 22:01:58 +00:00
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function euler120() {
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// Good luck!
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return true;
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}
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euler120();
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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