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A068425
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a(n) = floor(2^n*Pi).
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10
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1, 3, 6, 12, 25, 50, 100, 201, 402, 804, 1608, 3216, 6433, 12867, 25735, 51471, 102943, 205887, 411774, 823549, 1647099, 3294198, 6588397, 13176794, 26353589, 52707178, 105414357, 210828714, 421657428, 843314856, 1686629713
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OFFSET
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-1,2
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COMMENTS
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In other words, take the binary expansion of Pi, drop the decimal point and interpret the first n+2 bits as an integer.
Dubickas proves that infinitely many terms of this sequence are divisible by 2 or 3 (and hence infinitely many composites). - Charles R Greathouse IV, Feb 04 2016
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LINKS
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EXAMPLE
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The binary expansion of Pi (A004601) begins 1, 1. 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, ... so we get 1, 3, 6, 12, 25, 50, ...
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MATHEMATICA
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Table[Floor[2^n*Pi], {n, -1, 100}] (* G. C. Greubel, Mar 23 2018 *)
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PROG
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(Magma) R:= RealField(); [Floor(2^n*Pi(R)): n in [-1..100]]; // G. C. Greubel, Mar 23 2018
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CROSSREFS
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KEYWORD
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easy,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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