A125729 Numbers whose base 7 representation is 555....5.

0, 5, 40, 285, 2000, 14005, 98040, 686285, 4804000, 33628005, 235396040, 1647772285, 11534406000, 80740842005, 565185894040, 3956301258285, 27694108808000, 193858761656005, 1357011331592040, 9499079321144285

Offset

1,2

Links

Table of n, a(n) for n=1..20.

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

Formula

a(n) = 5*(7^(n-1)-1)/6 = 5*A023000(n-1).

a(n) = 7*a(n-1) + 5 for n > 1. - Vincenzo Librandi, Sep 30 2010

G.f.: 5*x^2 / ( (7*x-1)*(x-1) ). - R. J. Mathar, Sep 30 2013

Example

Base 7.............decimal
0........................0
5........................5
55......................40
555....................285
5555..................2000
55555................14005
555555...............98040
5555555.............686285
55555555...........4804000
555555555.........33628005
etc....................etc...

Maple

seq(5*(7^n-1)/6, n=0..21);

Crossrefs

Sequence in context: A229279 A124306 A124545 * A144069 A280158 A073505

Adjacent sequences: A125726 A125727 A125728 * A125730 A125731 A125732

Keyword

easy,nonn

Author

Zerinvary Lajos, Feb 02 2007

Status

approved