title: Python infinite recursion with formula
body: <pre><code>### Run the code below and understand the error messages
  ### Fix the code to sum integers from 1 up to k
  ### 
  
  def f(k):
      return f(k-1) + k
  print(f(10))
  </code></pre>
  
  <p>I am confused on how to fix this code while using recursion, I keep getting the error messages<br>
  <strong><em>[Previous line repeated 995 more times]
  RecursionError: maximum recursion depth exceeded</em></strong>
  Is there a simple way to fix this without using any while loops or creating more than 1 variable?</p>