def zero_absent(relation, initial_values, modulus):
initial = [value % modulus for value in initial_values]
curr = initial[:]
if 0 in initial:
return False
curr = [value % modulus for value in recurrence_next(relation, curr)]
while curr != initial:
if 0 in curr:
return False
curr = [value % modulus for value in recurrence_next(relation, curr)]
return True
def main(verbose=False):
relation = [1, 2]
h_values = [1, 3]
k_values = [1, 2]
count = 0
for i in range(2, 1000 + 1):
h_values = recurrence_next(relation, h_values)
k_values = recurrence_next(relation, k_values)
if len(str(h_values[1])) > len(str(k_values[1])):
count += 1
return count
def solutions(limit):
# We seek x_k^2 - 3y_k^2 = 4
# Where 3*n - sign = x_k
x_mult, y_mult, relation = get_recurrence([1, -3])
starting_points = all_values_on_form([1, -3], 4)
series = [start_to_series(initial, x_mult, 'x')
for initial in starting_points]
result = [pair[0] for pair in series
if pair[0] % 3 != 0 and pair[0] > 0]
while max(result) < 2 * limit:
next = [pair[1] for pair in series
if pair[1] % 3 != 0 and pair[1] > 0]
result.extend(next)
series = [recurrence_next(relation, values) for values in series]
# We seek perimeters n + n + (n + sign) = 3n + sign
# We currently have 3n - sign, so if we can determine the sign
# If value == 1 mod 3, then 3n - sign == 1, hence sign = -1
# and 3n + sign = 3n - 1 = value - 2
# If value == -1 mod 3, then 3n - sign == -1, hence sign = 1
# and 3n + sign = 3n + 1 = value + 2
result = sorted(((value + 2) if value % 3 == 2 else (value - 2))
for value in result)
# The first two solutions are 1-1-0 and 1-1-2, which are both degenerate
return [perimeter for perimeter in result
if perimeter < limit and perimeter not in (2, 4)]
def main(verbose=False):
a, b = 0, 2
running_sum = 0
while b <= 4000000:
running_sum += b
a, b = recurrence_next([1, 4], [a, b])
return running_sum
def main(verbose=False):
# we have h_(-1) = 1, k_(-1) = 0
# h_0/k_0 = 2
h_values = [1, 2]
k_values = [0, 1]
# The problem wants the 100th convergent which will
# be h_99/k_99. To get to this, we need the first 99
# values of a
a = reduce(operator.add, [[1,2*k,1] for k in range(1, 33 + 1)])
for a_i in a:
relation = [1, a_i]
h_values = recurrence_next(relation, h_values)
k_values = recurrence_next(relation, k_values)
h_99 = h_values[1]
k_99 = k_values[1]
reduced = h_99/(gcd(h_99, k_99))
return sum(int(dig) for dig in str(reduced))
def solutions(limit):
# We seek 5x_k^2 - y_k^2 = 1
# Where L = x_k
x_mult, y_mult, relation = get_recurrence([5, -1])
starting_points = all_values_on_form([5, -1], 1)
series = [start_to_series(initial, x_mult, 'x')
for initial in starting_points]
result = [pair[0] for pair in series if pair[0] > 1]
while len(result) < 2*limit:
next = [pair[1] for pair in series if pair[1] > 1]
result.extend(next)
series = [recurrence_next(relation, values) for values in series]
return sorted(result)[:limit]
def stable_expansion(digits, n):
values = continued_fraction_cycle(n)
h_values = [1, values[0]] # a_0
k_values = [0, 1]
cycle_length = len(values) - 1 # we only cycle over a_1,...,a_{k-1}
last = expanded_digits(h_values[1], k_values[1], digits)
index = 1
relation = [1, values[index]]
h_values = recurrence_next(relation, h_values)
k_values = recurrence_next(relation, k_values)
current = expanded_digits(h_values[1], k_values[1], digits)
while current != last:
index += 1
last = current
relative_index = ((index - 1) % cycle_length) + 1
# we want residues 1,..,k-1 instead of the traditional 0,...,k-2
relation = [1, values[relative_index]]
h_values = recurrence_next(relation, h_values)
k_values = recurrence_next(relation, k_values)
current = expanded_digits(h_values[1], k_values[1], digits)
return current
def golden_nuggets(limit):
# We seek 5x_k^2 - y_k^2 = 4
# Where 5n + 1 = y_k
x_mult, y_mult, relation = get_recurrence([5, -1])
starting_points = all_values_on_form([5, -1], 4)
series = [start_to_series(initial, y_mult, 'y')
for initial in starting_points]
nuggets = [pair[0] for pair in series
if pair[0] % 5 == 1 and pair[0] > 1]
while len(nuggets) < 2 * limit:
next = [pair[1] for pair in series
if pair[1] % 5 == 1 and pair[1] > 1]
nuggets.extend(next)
series = [recurrence_next(relation, values) for values in series]
return sorted([(value - 1) / 5 for value in nuggets])[:limit]
def main(verbose=False):
# y = 2T - 1, T > 10**12 implies the following:
LOWER_LIMIT = 2 * (10 ** 12) - 1
# We seek 2x^2 - y^2 = 1
x_mult, y_mult, relation = get_recurrence([2, -1])
starting_points = all_values_on_form([2, -1], 1)
series = [start_to_series(initial, y_mult, 'y')
for initial in starting_points]
result = [pair[0] for pair in series]
while max(result) <= LOWER_LIMIT:
result.extend([pair[1] for pair in series])
series = [recurrence_next(relation, values) for values in series]
min_y = min(y for y in result if y > LOWER_LIMIT)
min_x = sqrt((1 + min_y ** 2) / 2)
return int((min_x + 1) / 2)
