51 lines
1.1 KiB
Markdown
51 lines
1.1 KiB
Markdown
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---
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id: 5900f5151000cf542c510028
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title: 'Problem 425: Prime connection'
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challengeType: 5
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forumTopicId: 302095
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dashedName: problem-425-prime-connection
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---
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# --description--
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Two positive numbers A and B are said to be connected (denoted by "A ↔ B") if one of these conditions holds:
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(1) A and B have the same length and differ in exactly one digit; for example, 123 ↔ 173.
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(2) Adding one digit to the left of A (or B) makes B (or A); for example, 23 ↔ 223 and 123 ↔ 23.
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We call a prime P a 2's relative if there exists a chain of connected primes between 2 and P and no prime in the chain exceeds P.
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For example, 127 is a 2's relative. One of the possible chains is shown below: 2 ↔ 3 ↔ 13 ↔ 113 ↔ 103 ↔ 107 ↔ 127 However, 11 and 103 are not 2's relatives.
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Let F(N) be the sum of the primes ≤ N which are not 2's relatives. We can verify that F(103) = 431 and F(104) = 78728.
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Find F(107).
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# --hints--
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`euler425()` should return 46479497324.
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```js
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assert.strictEqual(euler425(), 46479497324);
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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 euler425() {
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return true;
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}
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euler425();
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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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