no duplicate sums

import itertools
import math
def is_prime(n):
    if n <= 1:
        return False
    elif n <= 3:
        return True
    elif n % 2 == 0 or n % 3 == 0:
        return False
    i = 5
    while i * i <= n:
        if n % i == 0 or n % (i + 2) == 0:
            return False
        i += 6
    return True
# Here I use odd primes only
def get_primes_up_to_N(N):
    primes = []
    num = 3
    while len(primes) < N:
        if is_prime(num):
            primes.append(num)
        num += 1
    return primes

N = 3
while True:
    primes = get_primes_up_to_N(N)
    # Generate N distinct primes raised to 6
    my_list = [prime ** 6 for prime in primes]
    combinations = list(itertools.combinations(my_list, 3))
    get_the_sums = []
    for i in combinations:
         get_the_sums.append(sum(i))
    #See if get_the_sums has no duplicates
    # If there is no duplicates then there should be no
    # collisions for subset sum
    print('The size of the Universe: ',N, 'No duplicate sums: ',len(get_the_sums) == len(set(get_the_sums)))
    N = N + 3
    if len(get_the_sums) != len(set(get_the_sums)):
        break