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#!/usr/bin/env python
import math
def is_prime(number):
# Return true or false if the number is a prime
if number < 2:
return False
for i in range(2, int(math.sqrt(number)) + 1):
if number % i == 0:
return False
# It's a prime
return True
def is_trunc_prime(number):
# Return true or false if the number and all it's left truncated
# parts is a prime. Start with the smallest figure first
n = str(number)
if '0' in n:
# A left-truncatable prime cannot contain a zero
return False
for i in range(len(n), 0, -1):
if not is_prime(int(n[i - 1:])):
return False
return True
def main():
solutions = []
number = 1
# Keep increasing number by one until we have twenty truncated prime
# numbers
while len(solutions) < 20:
if is_trunc_prime(number):
solutions.append(number)
number += 1
print(*solutions, sep=', ')
if __name__ == '__main__':
main()
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