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freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-278-linear-combinations-of-semiprimes.english.md
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1.3 KiB

id, challengeType, title, forumTopicId
id challengeType title forumTopicId
5900f4831000cf542c50ff95 5 Problem 278: Linear Combinations of Semiprimes 301928

Description

Given the values of integers 1 < a1 < a2 <... < an, consider the linear combination q1a1 + q2a2 + ... + qnan = b, using only integer values qk ≥ 0.

Note that for a given set of ak, it may be that not all values of b are possible. For instance, if a1 = 5 and a2 = 7, there are no q1 ≥ 0 and q2 ≥ 0 such that b could be 1, 2, 3, 4, 6, 8, 9, 11, 13, 16, 18 or 23.

In fact, 23 is the largest impossible value of b for a1 = 5 and a2 = 7. We therefore call f(5, 7) = 23. Similarly, it can be shown that f(6, 10, 15)=29 and f(14, 22, 77) = 195.

Find ∑ f(pq,pr,q*r), where p, q and r are prime numbers and p < q < r < 5000.

Instructions

Tests

tests:
  - text: <code>euler278()</code> should return 1228215747273908500.
    testString: assert.strictEqual(euler278(), 1228215747273908500);

Challenge Seed

function euler278() {
  // Good luck!
  return true;
}

euler278();

Solution

// solution required