A083423 a(n) = (5*3^n + (-3)^n)/6.

1, 2, 9, 18, 81, 162, 729, 1458, 6561, 13122, 59049, 118098, 531441, 1062882, 4782969, 9565938, 43046721, 86093442, 387420489, 774840978, 3486784401, 6973568802, 31381059609, 62762119218, 282429536481, 564859072962

Offset: 0

Author

Paul Barry, Apr 30 2003

Keywords

• easy
• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (0,9).

Crossrefs

Cf. A083424.

Programs

Mathematica

LinearRecurrence[{0,9},{1,2},30] (* Harvey P. Dale, Dec 04 2019 *)

Formula

From Reinhard Zumkeller, Mar 04 2011: (Start)

G.f.: (1+2x)/((1-3x)*(1+3x)).

E.g.f.: (5*exp(3x) + exp(-3x))/6.

a(n+3) = a(n+2)*a(n+1)/a(n). (End)

a(n) = 9*a(n-2). - Vincenzo Librandi, Mar 20 2011