--description--

A positive integer $n$ is called squarefree, if no square of a prime divides $n$, thus 1, 2, 3, 5, 6, 7, 10, 11 are squarefree, but not 4, 8, 9, 12.

How many squarefree numbers are there below $2^{50}$?

--hints--

squarefreeNumbers() should return 684465067343069.

assert.strictEqual(squarefreeNumbers(), 684465067343069);

--seed--

--seed-contents--

function squarefreeNumbers() {

  return true;
}

squarefreeNumbers();

--solutions--

// solution required