A198960 a(n) = 3*9^n-1.

2, 26, 242, 2186, 19682, 177146, 1594322, 14348906, 129140162, 1162261466, 10460353202, 94143178826, 847288609442, 7625597484986, 68630377364882, 617673396283946, 5559060566555522, 50031545098999706, 450283905890997362

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

[3*9^n-1: n in [0..20]];

Mathematica

CoefficientList[Series[2*(1 + 3*x)/(1 - 10*x + 9*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)
LinearRecurrence[{10,-9},{2,26},30] (* Harvey P. Dale, Dec 07 2024 *)

Formula

a(n) = 2*A096053(n).

a(n) = 9*a(n-1)+8, n>0.

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

G.f.: 2*(1 + 3*x)/(1 - 10*x + 9*x^2). - Vincenzo Librandi, Jan 03 2013