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A093141
Expansion of (1-6*x)/(1-10*x).
5
1, 4, 40, 400, 4000, 40000, 400000, 4000000, 40000000, 400000000, 4000000000, 40000000000, 400000000000, 4000000000000, 40000000000000, 400000000000000, 4000000000000000, 40000000000000000, 400000000000000000, 4000000000000000000, 40000000000000000000, 400000000000000000000
OFFSET
0,2
COMMENTS
Partial sums are A093140. A convex combination of 10^n and 0^n.
FORMULA
a(n) = 4*10^n/10 + 6*0^n/10.
a(n) = phi(10^n). - Paul Barry, Jul 02 2007
a(n) = 4*10^(n-1), n > 0. - Vincenzo Librandi, Aug 02 2010
From Elmo R. Oliveira, Aug 21 2024: (Start)
E.g.f.: (2*exp(10*x) + 3)/5.
a(n) = 10*a(n-1) for n > 1. (End)
MATHEMATICA
Table[EulerPhi[10^n], {n, 0, 40}] (* Vladimir Joseph Stephan Orlovsky, Nov 10 2009 *)
Join[{1}, NestList[10#&, 4, 20]] (* Harvey P. Dale, Apr 01 2018 *)
PROG
(PARI) Vec((1-6*x)/(1-10*x) + O(x^30)) \\ Michel Marcus, Jan 17 2015
CROSSREFS
Cf. A093140.
Sequence in context: A155641 A122652 A299867 * A220965 A278036 A221588
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 24 2004
EXTENSIONS
a(19)-a(21) from Elmo R. Oliveira, Aug 21 2024
STATUS
approved