title: Sequence with recurrence relation in C#
body: <p>The problem N°7</p>
  <p><img src="https://i.stack.imgur.com/iSrI0.jpg" alt="" /></p>
  <p>I'm new here, it's my first question, please be tolerant enough.</p>
  <p>What we've took so far are for and while loop.</p>
  <p>Edit: That's not a homework.
  I can't think of anything, we have had a similar problem in class and there we tried to switch the variables, and i tried that here, but it didn't work, and by the way it isn't a homework, that's a problem in an exam which i'm trying to prepare for it.</p>
  <p>And if you don't want to solve it, please tell me how to attack it, i always stumbles upon sequence problems.
  Thank you</p>