A110595 a(1)=5. For n > 1, a(n) = 4*5^(n-1) = A005054(n).

5, 20, 100, 500, 2500, 12500, 62500, 312500, 1562500, 7812500, 39062500, 195312500, 976562500, 4882812500, 24414062500, 122070312500, 610351562500, 3051757812500, 15258789062500, 76293945312500, 381469726562500

Offset

1,1

Comments

a(n) is the number of n-digit integers that contain only even digits (A014263). - Bernard Schott, Nov 11 2022

Links

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

Index entries for linear recurrences with constant coefficients, signature (5).

Formula

O.g.f.: 5*x*(1-x)/(1-5*x). - Better definition from R. J. Mathar, May 13 2008

Sum_{n>=1} 1/a(n) = 21/80. - Bernard Schott, Nov 11 2022

Mathematica

Join[{5}, NestList[5#&, 20, 20]] (* Harvey P. Dale, Jun 19 2013 *)
Rest[CoefficientList[Series[5 x (1 - x)/(1 - 5 x), {x, 0, 50}], x]] (* G. C. Greubel, Sep 01 2017 *)

Prog

(PARI) my(x='x+O('x^50)); Vec(5*x*(1-x)/(1-5*x)) \\ G. C. Greubel, Sep 01 2017

Crossrefs

Cf. A000351, A007091, A014263, A081604, A110591, A110592, A110593, A110594.

Sequence in context: A272218 A026118 A108509 * A369488 A092640 A165961

Adjacent sequences: A110592 A110593 A110594 * A110596 A110597 A110598

Keyword

easy,less,nonn

Author

Jonathan Vos Post, Jul 29 2005

Extensions

Better definition from R. J. Mathar, May 13 2008

Incorrect comment removed by Michel Marcus, Nov 11 2022

Status

approved