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A125823 Numbers whose base 7 representation is 4444....4. 1
0, 4, 32, 228, 1600, 11204, 78432, 549028, 3843200, 26902404, 188316832, 1318217828, 9227524800, 64592673604, 452148715232, 3165041006628, 22155287046400, 155087009324804, 1085609065273632, 7599263456915428, 53194844198408000, 372363909388856004, 2606547365721992032 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (8,-7).

FORMULA

a(n) = 2*(7^(n-1) - 1)/3 = 4*A023000(n-1).

a(n) = 7*a(n-1) + 4, with a(1)=0. - Vincenzo Librandi, Sep 30 2010

From G. C. Greubel, Aug 03 2019: (Start)

G.f.: 4*x^2/((1-x)*(1-7*x)).

E.g.f.: 2*(exp(7*x) - exp(x))/3. (End)

EXAMPLE

Base 7.................decimal

0.........................0

4.........................4

44.......................32

444.....................228

4444...................1600

44444.................11204

444444................78432

4444444..............549028

44444444............3843200

etc....................etc...

MAPLE

seq(4*(7^n-1)/6, n=0..21);

MATHEMATICA

2*(7^(Range[30]-1) -1)/3 (* G. C. Greubel, Aug 03 2019 *)

PROG

(PARI) vector(30, n, 2*(7^(n-1) -1)/3) \\ G. C. Greubel, Aug 03 2019

(MAGMA) [2*(7^(n-1) -1)/3: n in [1..30]]; // G. C. Greubel, Aug 03 2019

(Sage) [2*(7^(n-1) -1)/3 for n in (1..30)] # G. C. Greubel, Aug 03 2019

(GAP) List([1..30], n-> 2*(7^(n-1) -1)/3); # G. C. Greubel, Aug 03 2019

CROSSREFS

Cf. A023000.

Sequence in context: A099269 A316810 A299656 * A320366 A317560 A302742

Adjacent sequences:  A125820 A125821 A125822 * A125824 A125825 A125826

KEYWORD

easy,nonn

AUTHOR

Zerinvary Lajos, Feb 03 2007

EXTENSIONS

Terms a(21) onward added by G. C. Greubel, Aug 03 2019

STATUS

approved

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Last modified November 13 20:57 EST 2019. Contains 329106 sequences. (Running on oeis4.)