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Search: id:A060260
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| A060260 |
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Numbers n such that p(n), p(n+1) and p(n+2) have 10 as a primitive root, but p(n-1) and p(n+3) do not, where p(n)=A000040(n) is the n-th prime. |
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+0
4
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| 55, 75, 141, 164, 184, 199, 358, 371, 380, 432, 559, 702, 745, 808, 825, 858, 882, 1077, 1097, 1279, 1299, 1303, 1328, 1408, 1431, 1486, 1502, 1558, 1654, 1702, 1724, 1744, 1768, 1820, 1835, 1873, 1901, 1905, 1953, 1977, 2050, 2148, 2216, 2220, 2267
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A prime p has 10 as a primitive root iff the length of the period of the decimal expansion of 1/p is p-1.
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MATHEMATICA
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test[p_] := MultiplicativeOrder[10, p]===p-1; Select[Range[2, 2500], test[Prime[ # ]]&&test[Prime[ #+1]]&&test[Prime[ #+2]]&&!test[Prime[ #-1]]&&!test[Prime[ #+3]]&]
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CROSSREFS
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The corresponding primes p(n) are in A060261. Cf. A001913, A002371, A060259, A060262.
Sequence in context: A068899 A053719 A050781 this_sequence A152080 A119224 A135984
Adjacent sequences: A060257 A060258 A060259 this_sequence A060261 A060262 A060263
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KEYWORD
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nonn
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AUTHOR
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Jeff Burch (gburch(AT)erols.com), Mar 23 2001
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EXTENSIONS
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Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Jun 17 2002
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