26 lines
711 B
Markdown
26 lines
711 B
Markdown
---
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id: 5900f5311000cf542c510042
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title: 问题451:模逆
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challengeType: 5
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videoUrl: ''
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---
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# --description--
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考虑数字15.有八个正数小于15,它们与15:1,2,4,7,8,11,13,14相互作用。这些数模15的模数逆是:1,8,4 ,13,2,11,7,14因为1 \* 1 mod 15 = 1 2 \* 8 = 16 mod 15 = 1 4 \* 4 = 16 mod 15 = 1 7 \* 13 = 91 mod 15 = 1 11 \* 11 = 121 mod 15 = 1 14 \* 14 = 196 mod 15 = 1
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设I(n)是小于n-1的最大正数m,使得m modulo n的模逆与m本身相等。所以我(15)= 11。我(100)= 51和I(7)= 1。
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求3Σn≤2·107的ΣI(n)
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# --hints--
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`euler451()`应该返回153651073760956。
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```js
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assert.strictEqual(euler451(), 153651073760956);
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```
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# --solutions--
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