56 lines
1.1 KiB
Markdown
56 lines
1.1 KiB
Markdown
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---
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id: 5900f4451000cf542c50ff57
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challengeType: 5
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title: 'Problem 216: Investigating the primality of numbers of the form 2n2-1'
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videoUrl: ''
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localeTitle: 问题216：调查2n2-1形式的数字的素数
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---
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## Description
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<section id="description">考虑形式为t（n）= 2n2-1的数字t（n），其中n> 1.第一个这样的数字是7,17,31,49,71,97,127和161.事实证明只有49 = 7 * 7和161 = 7 * 23不是素数。对于n≤10000，有2202个数字t（n）是素数。 <p>对于n≤50,000,000，有多少个数t（n）是素数？ </p></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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tests:
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- text: <code>euler216()</code>应该返回5437849。
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testString: 'assert.strictEqual(euler216(), 5437849, "<code>euler216()</code> should return 5437849.");'
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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 euler216() {
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// Good luck!
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return true;
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}
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euler216();
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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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