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A083803
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Smallest number k such that the concatenations k 2n-1 and 2n-1 k are both primes, or 0 if n = 5m+3.
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0
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1, 1, 0, 1, 7, 3, 1, 0, 3, 7, 13, 11, 0, 1, 27, 1, 7, 0, 3, 7, 9, 39, 0, 9, 1, 19, 51, 0, 1, 3, 7, 1, 0, 3, 49, 9, 3, 0, 17, 19, 1, 9, 0, 7, 23, 1, 11, 0, 1, 1, 77, 1, 0, 33, 1, 109, 11, 0, 1, 3, 3, 1, 0, 7, 1, 51, 39, 0, 3, 21, 59, 21, 0, 13, 47, 1, 1, 0, 9, 7, 9, 19, 0, 29, 3, 37, 149, 0, 7, 21
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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COMMENTS
| Observation: Most of the members are prime or 1. what is the first composite entry?
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EXAMPLE
| a(19) = 7 as 197 and 719 both are prime, a(15) =0.
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CROSSREFS
| Sequence in context: A171535 A019648 A154159 * A136595 A111475 A010139
Adjacent sequences: A083800 A083801 A083802 * A083804 A083805 A083806
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KEYWORD
| base,nonn
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AUTHOR
| Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), May 08 2003
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EXTENSIONS
| More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Nov 30 2004
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