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Search: id:A066811
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| A066811 |
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Numbers n such that concatenation of odd numbers from 1 to n is a prime. |
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+0
2
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OFFSET
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1,1
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EXAMPLE
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E.g. a(2)=19 because 135791113151719 is a prime.
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MATHEMATICA
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p = ""; Do[p = p <> ToString[2*n+1]; If[PrimeQ[ToExpression[p]], Print[2*n+1]], {n, 0, 2569}] (Propper)
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CROSSREFS
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Cf. A005408, A000040.
Adjacent sequences: A066808 A066809 A066810 this_sequence A066812 A066813 A066814
Sequence in context: A108137 A102978 A107165 this_sequence A128069 A056246 A061427
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KEYWORD
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base,nonn
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com), Jan 20 2002
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EXTENSIONS
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5139 from Ryan Propper (rpropper(AT)stanford.edu), Aug 26 2005
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