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id	challengeType	title	forumTopicId
5900f4c71000cf542c50ffd8	5	Problem 346: Strong Repunits	302005

Description

The number 7 is special, because 7 is 111 written in base 2, and 11 written in base 6 (i.e. 710 = 116 = 1112). In other words, 7 is a repunit in at least two bases b > 1.

We shall call a positive integer with this property a strong repunit. It can be verified that there are 8 strong repunits below 50: {1,7,13,15,21,31,40,43}. Furthermore, the sum of all strong repunits below 1000 equals 15864.

Find the sum of all strong repunits below 1012.

Instructions

Tests

tests:
  - text: <code>euler346()</code> should return 336108797689259260.
    testString: assert.strictEqual(euler346(), 336108797689259260);

Challenge Seed

function euler346() {
  // Good luck!
  return true;
}

euler346();

Solution

// solution required

1.1 KiB Raw Blame History