A198768 a(n) = 9*5^n-1.

8, 44, 224, 1124, 5624, 28124, 140624, 703124, 3515624, 17578124, 87890624, 439453124, 2197265624, 10986328124, 54931640624, 274658203124, 1373291015624, 6866455078124, 34332275390624, 171661376953124, 858306884765624

Offset: 0

Author

Vincenzo Librandi, Oct 30 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (6,-5).

Crossrefs

Cf. A024049, A057651, A081655.

Programs

Magma

[9*5^n-1: n in [0..30]];

Mathematica

9 5^Range[0, 20] - 1 (* or *) LinearRecurrence[{6, -5}, {8, 44}, 20] (* Harvey P. Dale, Nov 01 2011 *)
CoefficientList[Series[(8 - 4 x)/(1 - 6 x + 5 x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)

Formula

a(n) = 5*a(n-1)+4.

a(n) = 6*a(n-1)-5*a(n-2), n > 1.

G.f.: (8 - 4*x)/(1 - 6*x + 5*x^2). - Vincenzo Librandi, Jan 03 2013