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
KEYWORD
nonn,easy
AUTHOR
Mark Dols, Jul 19 2010
EXTENSIONS
Name edited by Colin Barker, Oct 03 2015
STATUS
approved