login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A143769 Expansion of 3*x*(3*x+1)*(2*x-1) / ( (1+x)*(3*x^2+1) ). 1
-3, 0, 27, -18, -63, 36, 207, -126, -603, 360, 1827, -1098, -5463, 3276, 16407, -9846, -49203, 29520, 147627, -88578, -442863, 265716, 1328607, -797166, -3985803, 2391480, 11957427, -7174458, -35872263, 21523356, 107616807, -64570086, -322850403, 193710240 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All entries are multiples of 3.

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (-1,-3,-3)

FORMULA

a(n) = A141533(n+1)-2*A141533(n).

a(2n)+a(2n+1) = (-1)^n*A000244(n).

a(n) = (3/2) * ((2*(-1)^n - 3) * (-3)^floor(n/2) - 3*(-1)^n ). - Ralf Stephan, Aug 17 2013

MATHEMATICA

CoefficientList[Series[3 (3 x + 1) (2 x - 1) / ((1 + x) (3 x^2 + 1)), {x, 0, 40}], x] (* Vincenzo Librandi, Aug 17 2013 *)

LinearRecurrence[{-1, -3, -3}, {-3, 0, 27}, 40] (* Harvey P. Dale, Dec 26 2014 *)

PROG

(PARI) a(n)=3/2*((2*(-1)^n-3)*(-3)^floor(n/2)-3*(-1)^n); \\ Ralf Stephan, Aug 17 2013

(MAGMA) I:=[-3, 0, 27]; [n le 3 select I[n] else -Self(n-1)-3*Self(n-2) -3*Self(n-3): n in [1..50]]; // Vincenzo Librandi, Aug 17 2013

CROSSREFS

Sequence in context: A009777 A138543 A238104 * A190963 A296436 A215588

Adjacent sequences:  A143766 A143767 A143768 * A143770 A143771 A143772

KEYWORD

sign,easy

AUTHOR

Paul Curtz, Aug 31 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 19 20:38 EDT 2022. Contains 356231 sequences. (Running on oeis4.)