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A002280 a(n) = 6*(10^n - 1)/9. 25
0, 6, 66, 666, 6666, 66666, 666666, 6666666, 66666666, 666666666, 6666666666, 66666666666, 666666666666, 6666666666666, 66666666666666, 666666666666666, 6666666666666666, 66666666666666666 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n-1) = number of Fibonacci numbers F(k), k <= 10^n, which end in 0. a(1)=6 because there are 6 Fibonacci numbers up to 10^2 which end in 0. - Shyam Sunder Gupta and Benoit Cloitre, Aug 15 2002

a(n) = A178633(n)/A002283(n). - Reinhard Zumkeller, May 31 2010

a(n) is the total number of holes in a certain triangle fractal (start with 10 triangles, 6 holes) after n iterations. See illustration in links. - Kival Ngaokrajang, Feb 21 2015

LINKS

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

Kival Ngaokrajang, Illustration of initial terms

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

FORMULA

a(n) = 6*A002275(n).

a(n) = 10*a(n-1) + 6, with a(n)=0. - Paolo P. Lava, Jan 23 2009

From Jaume Oliver Lafont, Feb 03 2009: (Start)

G.f.: 6x/((1-x)(1-10x)).

a(n) = 11a(n-1) - 10a(n-2) with a(0)=0, a(1)=6. (End)

a(n) = a(n-1) + 6*10^(n-1) with a(0)=0. - Vincenzo Librandi, Jul 22 2010

MATHEMATICA

LinearRecurrence[{11, -10}, {0, 6}, 20] (* Harvey P. Dale, Dec 20 2012 *)

PROG

(PARI) a(n)=6*(10^n-1)/9 \\ Charles R Greathouse IV, Sep 24 2015

CROSSREFS

Different from A072912. Cf. A073548, etc.

Cf. A002275, A002276, A002277, A002278, A002279, A002281, A002282, A075415, A178631.

Sequence in context: A155630 A119125 A137120 * A073548 A073549 A119087

Adjacent sequences:  A002277 A002278 A002279 * A002281 A002282 A002283

KEYWORD

easy,nonn

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified November 16 19:17 EST 2019. Contains 329201 sequences. (Running on oeis4.)