A179556 a(1) = 10; a(n) = a(n-1)*10 - 2^(n-2).

10, 99, 988, 9876, 98752, 987504, 9875008, 98750016, 987500032, 9875000064, 98750000128, 987500000256, 9875000000512, 98750000001024, 987500000002048, 9875000000004096, 98750000000008192, 987500000000016384, 9875000000000032768, 98750000000000065536

Offset

1,1

Comments

79/80 = 0.9875.

Links

Colin Barker, Table of n, a(n) for n = 1..999

Index entries for linear recurrences with constant coefficients, signature (12,-20).

Formula

From Colin Barker, Oct 03 2015: (Start)

a(n) = 12*a(n-1) - 20*a(n-2) for n > 2.

G.f.: -x*(21*x - 10)/((2*x - 1)*(10*x - 1)). (End)

E.g.f.: (79*exp(10*x) + 5*exp(2*x) - 84)/80. - Stefano Spezia, Mar 04 2023

Mathematica

a[1] := 10; a[n_] := a[n] = 10 a[n - 1] - 2^(n - 2); Array[a@ # &, {20}] (* Michael De Vlieger, Oct 03 2015 *)

Prog

(PARI) Vec(-x*(21*x-10)/((2*x-1)*(10*x-1)) + O(x^30)) \\ Colin Barker, Oct 03 2015
(PARI) a(n) = if(n<2, 10, a(n-1)*10 - 2^(n-2));
vector(30, n, a(n)) \\ Altug Alkan, Oct 03 2015

Crossrefs

Cf. A000079, A011557.

Sequence in context: A004189 A322054 A179558 * A179477 A179555 A105694

Adjacent sequences: A179553 A179554 A179555 * A179557 A179558 A179559

Keyword

nonn,easy

Author

Mark Dols, Jul 19 2010

Extensions

Name edited by Colin Barker, Oct 03 2015

Status

approved