''' It was proposed by Christian Goldbach that every odd composite number can be written as the sum of a prime and twice a square. 9 = 7 + 2×12 15 = 7 + 2×22 21 = 3 + 2×32 25 = 7 + 2×32 27 = 19 + 2×22 33 = 31 + 2×12 It turns out that the conjecture was false. What is the smallest odd composite that cannot be written as the sum of a prime and twice a square? ''' # So I guess I just go past all odd non-prime numbers and keep subtracting all double squares that fit and see if the rest is a prime import math import numpy as np def sieve(n): assert n > 1 ns = [True] * n for i in range(2, math.ceil(np.sqrt(n))): if ns[i]: j = pow(i, 2) while j < n: ns[j] = False j = j + i return [i for i,val in enumerate(ns) if val][2:] def main(): print("Hello this is Patrick") end = 10000 primes = set(sieve(end)) for n in range(9, end, 2): termination = True if n not in primes: x = 1 while n - 2 * x*x > 0: if n - 2 * x*x in primes: termination = False break x += 1 if termination: print(n) break if __name__ == "__main__": main()