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A165246
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a(n) = (10^n+53)/9
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1
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7, 17, 117, 1117, 11117, 111117, 1111117, 11111117, 111111117, 1111111117, 11111111117, 111111111117, 1111111111117, 11111111111117, 111111111111117, 1111111111111117, 11111111111111117, 111111111111111117
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) are also n-1 units followed by a seven
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LINKS
| Markus Tervooren, Factorizations of (1)w7
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FORMULA
| a(n)=9*a(n-1)-8*a(n-2)+2*10^(n-2) [with a(1)=7, a(2)=17] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 02 2010]
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EXAMPLE
| a(3)=9*17-8*7+2*10=117; a(4)=9*117-8*17+2*10^2=1117 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 02 2010]
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MATHEMATICA
| Table[FromDigits[PadLeft[{7}, n, 1]], {n, 20}] (* From Harvey P. Dale, Oct 17 2011 *)
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CROSSREFS
| Sequence in context: A068172 A067185 A063384 * A118108 A147643 A061159
Adjacent sequences: A165243 A165244 A165245 * A165247 A165248 A165249
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KEYWORD
| easy,nonn
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AUTHOR
| Ivan Panchenko (ivanpan3(AT)gmail.com), Sep 10 2009
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