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Search: id:A105888
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| A105888 |
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a(n) = the smallest prime that, when written in binary, ends with the substring of 2n-1 in binary. |
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+0 1
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OFFSET
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1,1
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EXAMPLE
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2*5-1 = 9 is 1001 in binary. Looking at the binary numbers that end with 1001: 1001 = 9 in decimal is composite; 10010 = 18 in decimal is composite. But 10011 = 19 in decimal is prime. So a(5) = 19.
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MATHEMATICA
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pr=-16; Select[Prime[Range[200]], MultiplicativeOrder[pr, # ] == #-1 &]
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CROSSREFS
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A164022
Sequence in context: A142712 A147095 A161626 this_sequence A123632 A039868 A015723
Adjacent sequences: A105885 A105886 A105887 this_sequence A105889 A105890 A105891
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KEYWORD
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base,more,nonn
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Aug 08 2009
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