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Lucas-Lehmer test: Difference between revisions
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def is_prime(n) # P3 Prime Generator primality test
return n | 1 == 3 if n < 5 # n: 0,1,4|false, 2,3|true
return false if n.gcd(6) != 1 # for n a P3 prime candidate (pc)
pc1, pc2 = -1, 1 # use P3's prime candidates sequence
until (pc1 += 6) > Math.sqrt(n).to_i # pcs are only 1/3 of all integers
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