input: Write a python function to find the sum of Pythagorean triplet for a given number.
  assert pythagorean_triplet_sum(10) == 0
  assert pythagorean_triplet_sum(25) == 12
  assert pythagorean_triplet_sum(30) == 60
output: def pythagorean_triplet_sum(n):
      for a in range(1, n):
          for b in range(a + 1, n):
              c = n - a - b
              if c > 0 and a * a + b * b == c * c:
                  return a + b + c
      return 0