Brute force

Finding the difference between the sum of the squares and the square of the sum required two steps:

Find the sum of the squares:

From solution1.py:

def sum_of_squares(n):
    return sum(i**2 for i in range(1, n + 1))

And the square of the sum:

From solution1.py:

def square_of_sum(n):
    return sum(i for i in range(1, n + 1)) ** 2

Finally, just subtract the square of the sum by the sum of the squares:

From solution1.py:

def sum_square_difference(n=100):
    return square_of_sum(n) - sum_of_squares(n)