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A002279 a(n) = 5*(10^n - 1)/9. 24
0, 5, 55, 555, 5555, 55555, 555555, 5555555, 55555555, 555555555, 5555555555, 55555555555, 555555555555, 5555555555555, 55555555555555, 555555555555555, 5555555555555555, 55555555555555555 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Arithmetic mean of all n-digit odd numbers. E.g. a(2) = A.M. of {11,13,15,...97,99} = (11+99)/2 =55. - Amarnath Murthy, Aug 02 2005

a(n) = A178632(n)/A002283(n). - Reinhard Zumkeller, May 31 2010

LINKS

Ivan Panchenko, Table of n, a(n) for n = 0..200

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

FORMULA

a(n)=10*a(n-1)+5, with a(0)=0. - Paolo P. Lava, Jan 23 2009

a(n)=a(n-1)+5*10^(n-1) with a(0)=0; Also: a(n)=11*a(n-1)-10*a(n-2) with a(0)=0, a(1)=5. - Vincenzo Librandi, Jul 22 2010

G.f.: 5*x/((1 - x)*(1 - 10*x)). - Ilya Gutkovskiy, Feb 24 2017

MATHEMATICA

Table[FromDigits[PadRight[{}, n, 5]], {n, 0, 20}] (* Harvey P. Dale, Oct 05 2013 *)

PROG

(Maxima) A002279(n):=5*(10^n-1)/9$

makelist(A002279(n), n, 0, 30); /* Martin Ettl, Nov 08 2012 */

(PARI) a(n)=5*(10^n-1)/9 \\ Charles R Greathouse IV, Sep 24 2015

CROSSREFS

Cf. A002275, A002276, A002277, A002278, A002280, A002281, A002282, A075415.

Sequence in context: A043040 A226561 A062183 * A119292 A139258 A102312

Adjacent sequences:  A002276 A002277 A002278 * A002280 A002281 A002282

KEYWORD

easy,nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 18 09:55 EST 2019. Contains 329261 sequences. (Running on oeis4.)