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A165246 a(n) = (10^n + 53)/9 1
7, 17, 117, 1117, 11117, 111117, 1111117, 11111117, 111111117, 1111111117, 11111111117, 111111111117, 1111111111117, 11111111111117, 111111111111117, 1111111111111117, 11111111111111117, 111111111111111117 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(n) are also n-1 units followed by a seven.
LINKS
Markus Tervooren, Factorizations of (1)w7
FORMULA
a(n) = 9*a(n-1)-8*a(n-2)+2*10^(n-2) for n>2, a(1)=7, a(2)=17. [Vincenzo Librandi, Aug 02 2010]
a(n) = 11*a(n-1)-10*a(n-2). G.f.: -x*(60*x-7)/((x-1)*(10*x-1)). [Colin Barker, Jan 24 2013]
MATHEMATICA
Table[FromDigits[PadLeft[{7}, n, 1]], {n, 20}] (* Harvey P. Dale, Oct 17 2011 *)
CROSSREFS
Sequence in context: A262474 A284416 A063384 * A266382 A118108 A227506
KEYWORD
nonn,easy
AUTHOR
Ivan Panchenko, Sep 10 2009
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)