def factorizer(n) :
return factorize2( prime_factors2( n, primes_cached() ) )
NOTE: 2, 3, 5, and 7 are not considered to be truncatable primes
"""
from pe10 import primes_cached, prime_cache
from bisect import bisect_left
def index(lst, x):
'Locate the leftmost value exactly equal to x'
i = bisect_left(lst, x)
if i != len(lst) and lst[i] == x:
return i
return -1
is_prime = lambda p : index(prime_cache, p) != -1
def is_truncatable(p) :
if p < 10 : return False
digits = list(str(p))
return all( is_prime(int(''.join(digits[:i])))
and is_prime(int(''.join(digits[i:])))
for i in xrange(1,len(digits)))
#zip to take exactly 11 elements (takewhile would never find the 12th)
tp = list( p for i,p in zip( xrange(11), ( p for p in primes_cached() if is_truncatable(p)) ))
s = sum(tp)
assert s == 748317
