A125836 Numbers whose base 8 or octal representation is 555555555......5.

0, 5, 45, 365, 2925, 23405, 187245, 1497965, 11983725, 95869805, 766958445, 6135667565, 49085340525, 392682724205, 3141461793645, 25131694349165, 201053554793325, 1608428438346605, 12867427506772845, 102939420054182765

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 (9,-8).

Formula

a(n) = 5*(8^(n-1) -1)/7 = 5*A023001(n-1).

a(n) = 8*a(n-1) + 5, with a(1)=0. - Vincenzo Librandi, Sep 30 2010

G.f.: 5*x^2/( (1-x)*(1-8*x)). - R. J. Mathar, Sep 30 2013

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

a(n) = 5*A024088(n-1)/7.

E.g.f.: 5*(exp(8*x) - exp(x))/7. (End)

Example

Octal...............decimal
0........................0
5........................5
55......................45
555....................365
5555..................2925
55555................23405
555555..............187245
5555555............1497965
55555555..........11983725
555555555.........95869805
5555555555.......766958445
etc. ...............etc.

Maple

seq(5*(8^n-1)/7, n=0..30);

Mathematica

5*(8^(Range[30]-1) -1)/7 (* G. C. Greubel, Aug 03 2019 *)

Prog

(PARI) vector(30, n, 5*(8^(n-1) -1)/7) \\ G. C. Greubel, Aug 03 2019
(Magma) [5*(8^(n-1) -1)/7: n in [1..30]]; // G. C. Greubel, Aug 03 2019
(Sage) [5*(8^(n-1) -1)/7 for n in (1..30)] # G. C. Greubel, Aug 03 2019
(GAP) List([1..30], n-> 5*(8^(n-1) -1)/7); # G. C. Greubel, Aug 03 2019

Crossrefs

Cf. A023001, A024088.

Sequence in context: A268219 A272494 A185009 * A001260 A088505 A067403

Adjacent sequences: A125833 A125834 A125835 * A125837 A125838 A125839

Keyword

easy,nonn

Author

Zerinvary Lajos, Feb 03 2007

Status

approved