A172241 a(n) = (1/18)*(8^n - (-1)^n - 9).

0, 3, 28, 227, 1820, 14563, 116508, 932067, 7456540, 59652323, 477218588, 3817748707, 30541989660, 244335917283, 1954687338268, 15637498706147, 125099989649180, 1000799917193443, 8006399337547548, 64051194700380387

Offset

1,2

Comments

It appears that a(n) = A153234(3*n-1). - Bruno Berselli, May 03 2011

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (8, 1, -8).

Formula

G.f.: x^2*(3 + 4*x)/((1 - x)*(1 + x)*(1 - 8*x)). - Adapted to the offset by Bruno Berselli, May 03 2011

a(2*k) = 8*a(2*k-1) + 3 and a(2*k+1) = 8*a(2*k) + 4 for k>0, a(1)=0. - Yosu Yurramendi, Dec 30 2016

Maple

A172241:=n->(8^n-(-1)^n-9)/18: seq(A172241(n), n=1..30); # Wesley Ivan Hurt, May 02 2017

Mathematica

LinearRecurrence[{8, 1, -8}, {0, 3, 28}, 30] (* Harvey P. Dale, Oct 29 2023 *)

Prog

(PARI) a(n)=(8^n-(-1)^n-9)/18

Crossrefs

Sequence in context: A092637 A338689 A094296 * A321438 A341926 A323959

Adjacent sequences: A172238 A172239 A172240 * A172242 A172243 A172244

Keyword

nonn,easy

Author

Ralf Stephan, Nov 20 2010

Status

approved