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A088648
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a(1) = 1, then the smallest odd number not occurring earlier such that the concatenation a(r), a(s) is composite for all s > r.
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0
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1, 5, 11, 15, 19, 25, 35, 45, 55, 65, 75, 85, 95, 105, 115, 125, 135, 145, 155, 165, 175, 185, 195, 205, 215, 225, 235, 245, 255, 265, 275, 285, 295, 305, 315, 325, 335, 345, 355, 365, 375, 385, 395, 405, 415, 425, 435, 445, 455, 465, 475, 485, 495, 505, 515
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| The sequence is infinite with trivial terms of the form 10k+5. Subsidiary sequence: sequence of nontrivial terms. Conjecture: the subsidiary sequence is infinite.
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EXAMPLE
| a(5) = 19 as 119, 519,1119,1519, etc. are all composite.
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CROSSREFS
| Cf. A088647.
Sequence in context: A137003 A164355 A183227 * A075628 A036787 A187715
Adjacent sequences: A088645 A088646 A088647 * A088649 A088650 A088651
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KEYWORD
| base,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Oct 29 2003
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EXTENSIONS
| More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Aug 17 2005
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