A165246 - OEIS

A165246

a(n) = (10^n + 53)/9

7, 17, 117, 1117, 11117, 111117, 1111117, 11111117, 111111117, 1111111117, 11111111117, 111111111117, 1111111111117, 11111111111117, 111111111111117, 1111111111111117, 11111111111111117, 111111111111111117

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OFFSET

1,1

COMMENTS

a(n) are also n-1 units followed by a seven.

LINKS

Table of n, a(n) for n=1..18.

Markus Tervooren, Factorizations of (1)w7

Index entries for linear recurrences with constant coefficients, signature (11,-10).

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

Adjacent sequences: A165243 A165244 A165245 * A165247 A165248 A165249

KEYWORD

nonn,easy

AUTHOR

Ivan Panchenko, Sep 10 2009

STATUS

approved