<section id="description">
<p>Let f5(n) be the largest integer x for which 5x divides n.</p>
<p>For example, f5(625000) = 7.</p><p>Let T5(n) be the number of integers i which satisfy f5((2·i-1)!) &#x3C; 2·f5(i!) and 1 ≤ i ≤ n.
It can be verified that T5(103) = 68 and T5(109) = 2408210.</p>
<p>Find T5(1018).</p>
</section>

function euler383() {
  // Good luck!
  return true;
}

euler383();


index

Problem 383: Divisibility comparison between factorials

<code>euler383()</code> should return 22173624649806.