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A086680
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Number of primes < 4^n.
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3
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0, 2, 6, 18, 54, 172, 564, 1900, 6542, 23000, 82025, 295947, 1077871, 3957809, 14630843, 54400028, 203280221, 762939111, 2874398515, 10866266172, 41203088796, 156661034233, 597116381732, 2280998753949, 8731188863470, 33483379603407, 128625503610475, 494890204904784
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OFFSET
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0,2
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COMMENTS
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These numbers approximate the sum of primes < 2^n. The sum of primes < 2^20 = A130739(20) = 41162256126. The number of primes < 2^40 = 41203088796. The error is -0.000991993. From A007053, we have number of primes < 2^74 = 375744164937699609596 and sum of primes < 2^37 = 375743480734175191581 for an error of -0.0000018209325.
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LINKS
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FORMULA
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EXAMPLE
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a(2) = 6 because there are 6 primes, 2, 3, 5, 7, 11, and 13 that are < 4^2.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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