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A177108 a(n) = 4*(10^n-3). 1
28, 388, 3988, 39988, 399988, 3999988, 39999988, 399999988, 3999999988, 39999999988, 399999999988, 3999999999988, 39999999999988, 399999999999988, 3999999999999988, 39999999999999988, 399999999999999988 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

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

FORMULA

G.f.: 4*x*(7+20*x) / ( (10*x-1)*(x-1) ). a(n)=4*A173833(n). - R. J. Mathar, Jan 06 2011

a(n) = a(n-1) +36*10^(n-1) = 10*a(n-1) +108 = 11*a(n-1) -10*a(n-2). - Vincenzo Librandi, Jul 15 2012

MATHEMATICA

CoefficientList[Series[4*(7+20*x)/((10*x-1)*(x-1)), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 15 2012 *)

4(10^Range[20]-3) (* or *) LinearRecurrence[{11, -10}, {28, 388}, 20] (* Harvey P. Dale, Sep 25 2012 *)

PROG

(MAGMA) [4*(10^n-3): n in [1..20]]; // Vincenzo Librandi, Jul 15 2012

CROSSREFS

Sequence in context: A022623 A077507 A130608 * A283637 A126921 A035709

Adjacent sequences:  A177105 A177106 A177107 * A177109 A177110 A177111

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 15 2010

STATUS

approved

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Last modified July 22 20:45 EDT 2019. Contains 325226 sequences. (Running on oeis4.)