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Factors of a Mersenne number: Difference between revisions
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kp2 = p2 = 2.to_big_i * p
while (kp2 - 1) ** 2 < mers_num
q = kp2 + 1 # return q if it's a factor
return q if [1, 7].includes?(q % 8) && prime?(q) && (powmod(2, p, q) == 1)
kp2 += p2
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