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Search: id:A075612
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| A075612 |
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a(1) = 1, a(n) = smallest prime number not already used such that concatenation of a(k) and a(n) is composite for all k = 1 to n-1. |
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+0
1
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| 1, 2, 5, 17, 19, 43, 61, 127, 149, 199, 263, 349, 353, 461, 587, 769, 809, 883, 1009, 1303, 1619, 2179, 2207, 2467, 2591, 2593, 2909, 3019, 3517, 3821, 3853, 3989, 5669, 6121, 8011, 8273, 8563, 9127, 10163, 10639, 12781, 13009, 13577, 13619, 13907
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Is the sequence finite? Surprisingly it contains the finite sequence A020608 (2,5,17,19,43,61).
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EXAMPLE
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a(4) = 17 because 117, 217, and 517 are all composite.
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CROSSREFS
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Cf. A075611.
Sequence in context: A104247 A095287 A020608 this_sequence A041283 A042049 A069689
Adjacent sequences: A075609 A075610 A075611 this_sequence A075613 A075614 A075615
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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 28 2002
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EXTENSIONS
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More terms from David Wasserman (dwasserm(AT)earthlink.net), Jan 21 2005
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