def eratosthenes(n):
N=range(n+1)
z=[0]*(n/2)
for i in range(2, int(n**.5)+1):
if N[i]:
N[i*i::i] = z[:(n/i)-i+1]
return filter(None, N[2:])
def eratosthenes(n):
N=range(n+1)
z=[0]*(n/2)
for i in range(2, int(n**.5)+1):
if N[i]:
N[i*i::i] = z[:(n/i)-i+1]
return filter(None, N[2:])