51 lines
976 B
Markdown
51 lines
976 B
Markdown
---
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id: 5900f5271000cf542c51003a
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title: 'Problema 443: sequenza GCD'
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challengeType: 5
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forumTopicId: 302115
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dashedName: problem-443-gcd-sequence
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---
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# --description--
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Sia $g(n)$ una sequenza definita come segue:
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$$\begin{align} & g(4) = 13, \\\\
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& g(n) = g(n-1) + gcd(n, g(n - 1)) \text{ for } n > 4. \end{align}$$
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I primi valori sono:
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$$\begin{array}{l} n & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11 & 12 & 13 & 14 & 15 & 16 & 17 & 18 & 19 & 20 & \ldots \\\\
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g(n) & 13 & 14 & 16 & 17 & 18 & 27 & 28 & 29 & 30 & 31 & 32 & 33 & 34 & 51 & 54 & 55 & 60 & \ldots \end{array}$$
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Ti viene dato che $g(1\\,000) = 2\\,524$ and $g(1\\,000\\,000) = 2\\,624\\,152$.
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Trova $g({10}^{15})$.
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# --hints--
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`gcdSequence()` dovrebbe restituire `2744233049300770`.
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```js
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assert.strictEqual(gcdSequence(), 2744233049300770);
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```
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# --seed--
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## --seed-contents--
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```js
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function gcdSequence() {
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return true;
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}
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gcdSequence();
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```
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# --solutions--
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```js
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// solution required
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```
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