title: code for the sum of a Fibonacci sequence doesnt give the correct sum
body: <p>I wrote this code to calculate the sum of any n that I input for the Fibonacci sequence. </p>
  
  <pre><code>def fib(n):
      if n==0:
          return 0
      elif n==1:
          return 1
      elif n==2:
          return 2
      else:
          num = fib(n-1) + fib(n-2)
          return num 
      return sum(num)
  
  fib(7)
  </code></pre>
  
  <p>This produces an output of 21 when it's supposed to produce an outcome of 20? It always seems to output a sum of one more than the actual sum </p>