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joehakimrahme/prime4.py

Created July 4, 2012 16:00
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isprime - 6k +/- 1
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prime4.py
import math.sqrt as sqrt
def prime4(n):
if n<=1:
return False
if n % 2 == 0 and n != 2:
return False
if n % 3 == 0 and n != 3:
return False
# Limiting the tests to the 6k +/- 1 numbers
for i in (x for x in xrange(3, int(sqrt(n)), 2)
if x % 6 == 1 or x % 6 == 5):
if n % i == 0:
return False
return True
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