def right_truncatable_harshad_numbers():
for ex in takewhile(lambda x: x <= EXPONENT, count(start=1)):
for h in harshad_numbers[ex - 1]:
k = 10 * h
for d in range(10):
candidate = k + d
if not (candidate % digit_sum(candidate)):
harshad_numbers[ex].append(candidate)
yield candidate
def is_strong(h):
return is_prime(h / digit_sum(h))
def convergents_of_e():
length = 100
chain_fraction = prepare_quotient_list(length)
approximation = reversed_euklid(chain_fraction)
return digit_sum(approximation.numerator)