A014923 a(1) = 1, a(n) = n*9^(n-1) + a(n-1).

1, 19, 262, 3178, 35983, 390277, 4110364, 42374116, 429794605, 4303999495, 42658627906, 419231343214, 4090815317467, 39676936914073, 382828823738488, 3677086937252872, 35178430147734169

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (19,-99,81).

Formula

a(1)=1, a(2)=19, a(n) = 18*a(n-1) - 81*a(n-2) + 1. - Vincenzo Librandi, Oct 23 2012

G.f.: x/((1 - x)*(1 - 9*x)^2). - Vincenzo Librandi, Oct 23 2012

Mathematica

CoefficientList[Series[1/((1 - x)(1 - 9*x)^2), {x, 0, 40}], x] (* Vincenzo Librandi, Oct 23 2012 *)

Prog

(Magma) I:=[1, 19]; [n le 2 select I[n] else 18*Self(n-1) - 81*Self(n-2) + 1: n in [1..30]]; // Vincenzo Librandi, Oct 23 2012
(PARI) Vec(x/((1 - x)*(1 - 9*x)^2) + O(x^30)) \\ Jinyuan Wang, Mar 11 2020

Crossrefs

Sequence in context: A335515 A017917 A016308 * A081036 A244652 A142817

Adjacent sequences: A014920 A014921 A014922 * A014924 A014925 A014926

Keyword

nonn,easy

Author

Olivier Gérard

Status

approved