def main(n):
limit = (2 * ((n + 1)**2)) - 1
p = Prime()
primes = p.sieve(limit)
d = {
x:True for x in primes
}
res = []
for i in range(2, n + 1):
t = (2 * (i**2)) - 1
if t in d:
res.append(t)
return len(res)
def main(n):
limit = (2 * ((n + 1)**2)) - 1
p = Prime()
primes = p.sieve(limit)
d = {
x:True for x in primes
}
res = []
for i in range(2, n + 1):
t = (2 * (i**2)) - 1
if t in d:
res.append(t)
return len(res)
