login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A170955 a(n) = 10^n - 9. 6
1, 91, 991, 9991, 99991, 999991, 9999991, 99999991, 999999991, 9999999991, 99999999991, 999999999991, 9999999999991, 99999999999991, 999999999999991, 9999999999999991, 99999999999999991, 999999999999999991 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 10 of A193871. - Omar E. Pol, Aug 22 2011

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..100

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

FORMULA

a(n) = 10*a(n-1) + 81 for n>1, a(1)=1.

G.f.: x*(1+80*x) / ( (10*x-1)*(x-1) ). - R. J. Mathar, Aug 24 2011

MATHEMATICA

CoefficientList[Series[(1 + 80*x)/(1 - 11*x + 10*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 06 2013 *)

LinearRecurrence[{11, -10}, {1, 91}, 20] (* Harvey P. Dale, Aug 20 2015 *)

10^Range[1, 25] - 9 (* Vincenzo Librandi, Jan 03 2016 *)

PROG

(MAGMA) [10^n-9: n in [1..30]]; // Vincenzo Librandi, Feb 06 2013

(PARI) a(n)=10^n-9 \\ Charles R Greathouse IV, Oct 07 2015

CROSSREFS

Cf. A093177.

Sequence in context: A254519 A185375 A036526 * A020316 A221815 A195221

Adjacent sequences:  A170952 A170953 A170954 * A170956 A170957 A170958

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Feb 26 2010

EXTENSIONS

Typo in formula corrected by Jon E. Schoenfield, Jun 19 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 22 06:05 EST 2019. Contains 320389 sequences. (Running on oeis4.)