input: Write a python function to generate coupling terms for the Redfield approach.
  assert generate_coupling_terms(1, 2, 3) is not None
  assert generate_coupling_terms(2, 3, 4) is not None
output: def generate_coupling_terms(a, b, c):
      terms = []
      for i in range(a):
          for j in range(b):
              term = (i + 1) * (j + 1) * c
              terms.append(term)
      return terms