login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A246313 G.f.: (-1+6*x)/(1-3*x-2*x^2). 1
-1, 3, 7, 27, 95, 339, 1207, 4299, 15311, 54531, 194215, 691707, 2463551, 8774067, 31249303, 111296043, 396386735, 1411752291, 5028030343, 17907595611, 63778847519, 227151733779, 809012896375, 2881342156683, 10262052262799, 36548841101763, 130170627830887, 463609565696187, 1651169952750335 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Encountered during the analysis of a certain cellular automaton.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,2).

FORMULA

a(n) = 3*a(n-1) + 2*a(n-2) with a(0)=-1, a(1)=3.

a(n) = -(17+9*sqrt(17))/34*(3/2-sqrt(17)/2)^n+(-17+9*sqrt(17))/34*(3/2+sqrt(17)/2)^n.  For n >= 3, a(n) = round(-17+9*sqrt(17))/34*(3/2+sqrt(17)/2)^n). - Robert Israel, Aug 27 2014

a(n) = 6*A007482(n-1)+A007482(n). - R. J. Mathar, Feb 27 2019

MAPLE

a:= LRETools[REtoproc](a(n)=3*a(n-1)+2*a(n-2), a(n), {a(0)=-1, a(1)=3}):

seq(a(i), i=0..100); # Robert Israel, Aug 27 2014

MATHEMATICA

CoefficientList[Series[(6 x - 1)/(1 - 3 x - 2 x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Aug 27 2014 *)

PROG

(MAGMA) I:=[-1, 3]; [n le 2 select I[n] else 3*Self(n-1)+2*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Aug 27 2014

(PARI) Vec((-1+6*x)/(1-3*x-2*x^2)+O(x^99)) \\ Charles R Greathouse IV, Sep 02 2014

CROSSREFS

Sequence in context: A081562 A216174 A260464 * A003083 A062795 A062363

Adjacent sequences:  A246310 A246311 A246312 * A246314 A246315 A246316

KEYWORD

sign,easy

AUTHOR

N. J. A. Sloane, Aug 26 2014

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 15 22:02 EST 2019. Contains 330012 sequences. (Running on oeis4.)