title: python why doesnt this work
body: <pre><code>from math import factorial
  import math
  def get_bernoulli(n):
      b = 0
      sum = 0
      for k in range (0, n-1):
          part = (factorial(n)) / factorial(k) * factorial(n+1 - k)))*b
          sum += part
          b = -(1/n+1)*sum
  </code></pre>
  
  <p>pycharm is complaining about n k and b. It displays unsolved reference.  what does this means? </p>