def is_truncated_prime(n): str_n = str(n) for i, _ in enumerate(str_n): try: if not (is_prime(int(str_n[i:])) and is_prime(int(str_n[:i]))): return False except ValueError: continue return True
def solve(): prime_count = 3 side_length = 2 count = 9 while prime_count / (2 * side_length + 1) > 0.10: side_length += 2 for i in range(3): count += side_length if is_prime(count): prime_count += 1 count += side_length return side_length + 1
def solve(): # Only test for 7 digit pandigitals, as all 8/9-digit pandigitals are divisible by 3 for pandigital in sorted(pandigital_list(7), reverse=True): pandigital = int(pandigital) if is_prime(pandigital): return pandigital