A016172 Expansion of 1/((1-6x)(1-9x)).

1, 15, 171, 1755, 17091, 161595, 1501011, 13789035, 125780931, 1142106075, 10339420851, 93417584715, 842935044771, 7599476096955, 68473649036691, 616733026314795, 5553418346740611, 49997691780110235

Offset

0,2

Links

Table of n, a(n) for n=0..17.

Index entries for linear recurrences with constant coefficients, signature (15,-54).

Formula

a(n) = (9^(n+1)-6^(n+1))/3. - Lambert Klasen (lambert.klasen(AT)gmx.net), Feb 05 2005

a(0)=1, a(n) = 9*a(n-1) + 6^n. - Vincenzo Librandi, Feb 09 2011

a(0)=1, a(1)=15, a(n) = 15*a(n-1) - 54*a(n-2). - Vincenzo Librandi, Feb 09 2011

Mathematica

Join[{a=1, b=15}, Table[c=15*b-54*a; a=b; b=c, {n, 60}]] (* Vladimir Joseph Stephan Orlovsky, Feb 01 2011 *)
CoefficientList[Series[1/((1-6x)(1-9x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{15, -54}, {1, 15}, 30] (* Harvey P. Dale, Oct 07 2015 *)

Prog

(PARI) Vec(1/((1-6*x)*(1-9*x))+O(x^99)) \\ Charles R Greathouse IV, Sep 26 2012

Crossrefs

Sequence in context: A339770 A240276 A206600 * A016225 A058687 A206594

Adjacent sequences: A016169 A016170 A016171 * A016173 A016174 A016175

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved