freeCodeCamp

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id	challengeType	title	forumTopicId
5900f49b1000cf542c50ffad	5	Problem 302: Strong Achilles Numbers	301956

Description

A positive integer n is powerful if p2 is a divisor of n for every prime factor p in n.

A positive integer n is a perfect power if n can be expressed as a power of another positive integer.

A positive integer n is an Achilles number if n is powerful but not a perfect power. For example, 864 and 1800 are Achilles numbers: 864 = 25·33 and 1800 = 23·32·52.

We shall call a positive integer S a Strong Achilles number if both S and φ(S) are Achilles numbers.1 For example, 864 is a Strong Achilles number: φ(864) = 288 = 25·32. However, 1800 isn't a Strong Achilles number because: φ(1800) = 480 = 25·31·51.

There are 7 Strong Achilles numbers below 104 and 656 below 108.

How many Strong Achilles numbers are there below 1018?

1 φ denotes Euler's totient function.

Instructions

Tests

tests:
  - text: <code>euler302()</code> should return 1170060.
    testString: assert.strictEqual(euler302(), 1170060);

Challenge Seed

function euler302() {
  // Good luck!
  return true;
}

euler302();

Solution

// solution required

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