title: Calculating very large power
body: <p>I want to calculate for very large numbers like n = 10^15.</p>
  <p>Somehow I can't, because of OverflowError.</p>
  <pre><code>xd = lambda n : ((((5+ sqrt(17)) * ((3 + sqrt(17)) ** n)) - ((5-sqrt(17))* ((3 - sqrt(17)) ** n)))/((2 ** (n+1)) * sqrt(17)))
  </code></pre>
  <p>even for n=1000, it wouldn't be calculated.</p>
  <p>Though, I should mention that I want the modular of it (1000000007)</p>
  <p>What would be the solution?</p>