def mobius(n):
if n == 1:
return 1
k = 0
for p, e in factor(n):
if e > 1:
return 0
k += 1
return (-1) ** int(k % 2 == 1)
def pisano(m):
pi = 1
for p, e in nt.factor(m):
pi = lcm(pi, _pisano(p)*p**(e-1))
return pi
