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A110595
a(1)=5. For n > 1, a(n) = 4*5^(n-1) = A005054(n).
2
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
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
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