The arithmetic sequence, 1487, 4817, 8147, in which each of the terms increases by 3330, is unusual in two ways: (i) each of the three terms are prime, and, (ii) each of the 4-digit numbers are permutations of one another.
There are no arithmetic sequences made up of three 1-, 2-, or 3-digit primes, exhibiting this property, but there is one other 4-digit increasing sequence.
What 12-digit number do you form by concatenating the three terms in this sequence?
import math
import itertools
PRIME_LIST = []
result = {}
def is_Prime(number):
if number < 2:
return False
for x in range(2, int(math.sqrt(number)) + 1):
if number % x == 0:
return False
return True
for i in range(1000, 10000):
if is_Prime(i):
PRIME_LIST.append(i)
for prime in PRIME_LIST:
key_list = [eval(i) for i in str(prime)]
key_list.sort()
key_str = str(key_list)
if key_str in result:
result[key_str].append(prime)
else:
result[key_str] = [prime]
for key in result.keys():
if len(result[key]) < 3:
result.pop(key)
for key in result.keys():
for a, b, c in list(itertools.combinations(result[key], 3)):
if c - b == b - a:
print a, b, c
原来很理想化把if len(result[key]) < 3:这里弄成了等于，怎么都求不出来