2015-02-20 09:02:09 -05:00
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require "prime"
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class Integer
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def popcount
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2017-09-23 10:01:46 +02:00
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to_s(2).count("1") #Ruby 2.4: digits(2).count(1)
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2015-02-20 09:02:09 -05:00
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end
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def pernicious?
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popcount.prime?
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end
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end
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p 1.step.lazy.select(&:pernicious?).take(25).to_a
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p ( 888888877..888888888).select(&:pernicious?)
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