id	title	challengeType	forumTopicId	dashedName
5900f4451000cf542c50ff57	Problem 216: Investigating the primality of numbers of the form 2n2-1	5	301858	problem-216-investigating-the-primality-of-numbers-of-the-form-2n2-1

--description--

Consider numbers t(n) of the form t(n) = 2n2-1 with n > 1.

The first such numbers are 7, 17, 31, 49, 71, 97, 127 and 161.

It turns out that only 49 = 7*7 and 161 = 7*23 are not prime.

For n ≤ 10000 there are 2202 numbers t(n) that are prime.

How many numbers t(n) are prime for n ≤ 50,000,000 ?

--hints--

euler216() should return 5437849.

assert.strictEqual(euler216(), 5437849);

function euler216() {

  return true;
}

euler216();

// solution required