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Search: id:A105042
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| A105042 |
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Numbers n such that 10*n - 1 is prime. |
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1
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| 2, 3, 6, 8, 9, 11, 14, 15, 18, 20, 23, 24, 27, 35, 36, 38, 39, 41, 42, 44, 45, 48, 50, 51, 57, 60, 62, 66, 71, 72, 74, 77, 81, 83, 84, 86, 92, 93, 101, 102, 104, 105, 107, 111, 113, 123, 125, 126, 128, 129, 132, 140, 141, 143, 144, 146, 149, 150, 155, 156, 158, 161, 162
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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a(k)=(A030433(k)+1)/10. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 08 2009]
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EXAMPLE
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If n=2, then 10*n - 1 = 19 (prime).
If n=18, then 10*n - 1 = 179 (prime).
If n=36, then 10*n - 1 = 359 (prime).
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MAPLE
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a := proc (n) if isprime(10*n-1) = true then n else end if end proc: seq(a(n), n = 1 .. 200); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 02 2009]
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MATHEMATICA
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a={}; Do[x=10*n-1; If[PrimeQ[x], AppendTo[a, n]], {n, 10^2}]; a - Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 29 2008
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CROSSREFS
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Sequence in context: A093510 A013948 A013952 this_sequence A092114 A032711 A047244
Adjacent sequences: A105039 A105040 A105041 this_sequence A105043 A105044 A105045
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KEYWORD
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nonn
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AUTHOR
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Parthasarathy Nambi (PachaNambi(AT)yahoo.com), Apr 03 2005
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EXTENSIONS
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Extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 02 2009
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