A198969 (11*9^n-1)/2.

5, 49, 445, 4009, 36085, 324769, 2922925, 26306329, 236756965, 2130812689, 19177314205, 172595827849, 1553362450645, 13980262055809, 125822358502285, 1132401226520569, 10191611038685125, 91724499348166129, 825520494133495165

Offset: 0

Author

Vincenzo Librandi, Nov 01 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 (10,-9).

Programs

Magma

[(11*9^n-1)/2: n in [0..20]]

Mathematica

CoefficientList[Series[(5 - x)/(1 - 10*x + 9*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)
LinearRecurrence[{10,-9},{5,49},20] (* Harvey P. Dale, Oct 16 2021 *)

Formula

a(n) = 9*a(n-1)+4. a(n) = 10*a(n-1)-9*a(n-2), n>1.

G.f.: (5 - x)/(1 - 10*x + 9*x^2). - Vincenzo Librandi, Jan 03 2013