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Search: id:A078294
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| A078294 |
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Smallest multiple of n in which the most significant occurrence of the digit string of n is preceded and followed by the digit string of (n-1) and (n+1) as can be seen in the forward concatenation of the natural numbers. |
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+0
1
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| 12, 1230, 234, 3452, 4560, 5670, 6783, 7896, 8910, 910110, 101112, 1112136, 1213147, 1314152, 1415160, 1516177, 16171811, 1718190, 18192006, 19202100, 2021229, 2122230, 2223249, 2324256, 25262700, 2627289, 2728292, 28293009
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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The following inequality obviously holds for n > 1: a(n) >= (n-1)*10^(floor(1+log n) + floor(1+log(n+1))) + n*10^(floor(1+log(n+1))) + n + 1 where log is taken base 10, not base e. - Sam Alexander (amnalexander(AT)yahoo.com), Oct 19 2003
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EXAMPLE
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a(1) = 12 = 012, a(9) = 8910, a(13) = 1213147, 13 is sandwiched between 12 and 14.
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CROSSREFS
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Sequence in context: A033564 A054351 A080814 this_sequence A009155 A078296 A137343
Adjacent sequences: A078291 A078292 A078293 this_sequence A078295 A078296 A078297
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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), Nov 26 2002
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EXTENSIONS
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Corrected and extended by Sam Alexander (amnalexander(AT)yahoo.com), Oct 19 2003
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