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Search: id:A087604
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| A087604 |
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Smallest k such that n times concatenation of k with itself followed by a 3 is a prime, or 0 if no such number exists. |
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+0
8
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| 1, 1, 0, 1, 4, 0, 2, 1, 0, 1, 4, 0, 37, 7, 0, 17, 149, 0, 185, 7, 0, 73, 1, 0, 5, 47, 0, 38, 4, 0, 4, 133, 0, 52, 2, 0, 194, 46, 0, 37, 29, 0, 29, 25, 0, 19, 14, 0, 74, 8, 0, 19, 20, 0, 442, 83, 0, 358, 211, 0, 16, 298, 0, 260, 5, 0, 305, 71, 0, 8, 323, 0, 5, 109, 0, 8, 68, 0, 767, 367
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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Trivially a(3n) = 0. Conjecture: no other term is zero.
Either a(13)=0 or a(13)>36. This sequence contains no positive multiples of 3. If a(m) is of the form bbb...b (repeated k times) then a(km) <= b. - Sam Alexander (amnalexander(AT)yahoo.com), Oct 20 2003
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EXAMPLE
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a(5) = 4 as 444443 is a prime. but 111113,222223,333333 are not.
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CROSSREFS
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Cf. A086920, A087605, A087606, A087607, A087608, A087609, A087610.
Sequence in context: A067565 A010635 A019200 this_sequence A090538 A109157 A123314
Adjacent sequences: A087601 A087602 A087603 this_sequence A087605 A087606 A087607
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 18 2003
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EXTENSIONS
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More terms from Sam Alexander (amnalexander(AT)yahoo.com), Oct 20 2003
More terms from Ray G. Opao (1260(AT)email.com), Apr 15 2004
More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jun 16 2005
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