freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-167-investigating-ulam-sequences.english.md

id, challengeType, title, forumTopicId

id	challengeType	title	forumTopicId
5900f4141000cf542c50ff26	5	Problem 167: Investigating Ulam sequences	301801

Description

For two positive integers a and b, the Ulam sequence U(a,b) is defined by U(a,b)1 = a, U(a,b)2 = b and for k > 2, U(a,b)k is the smallest integer greater than U(a,b)(k-1) which can be written in exactly one way as the sum of two distinct previous members of U(a,b). For example, the sequence U(1,2) begins with 1, 2, 3 = 1 + 2, 4 = 1 + 3, 6 = 2 + 4, 8 = 2 + 6, 11 = 3 + 8; 5 does not belong to it because 5 = 1 + 4 = 2 + 3 has two representations as the sum of two previous members, likewise 7 = 1 + 6 = 3 + 4. Find ∑U(2,2n+1)k for 2 ≤ n ≤10, where k = 1011.

Instructions

Tests

tests:
  - text: <code>euler167()</code> should return 3916160068885.
    testString: assert.strictEqual(euler167(), 3916160068885);

Challenge Seed

function euler167() {
  // Good luck!
  return true;
}

euler167();

Solution

// solution required