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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A077987 Expansion of 1/(1+2*x-x^2+2*x^3). 2
1, -2, 5, -14, 37, -98, 261, -694, 1845, -4906, 13045, -34686, 92229, -245234, 652069, -1733830, 4610197, -12258362, 32594581, -86667918, 230447141, -612751362, 1629285701, -4332217046, 11519222517, -30629233482, 81442123573, -216551925662, 575804441861, -1531045056530 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (-2,1,-2).

FORMULA

a(n) = -2*a(n-1)+a(n-2)-2*a(n-3) with a(0)=1, a(1)=-2, a(2)=5. - Harvey P. Dale, Dec 27 2013

a(n) = (-1)^n * A077938(n). - G. C. Greubel, Jun 25 2019

MATHEMATICA

CoefficientList[Series[1/(1+2x-x^2+2x^3), {x, 0, 40}], x] (* or *) LinearRecurrence[{-2, 1, -2}, {1, -2, 5}, 40] (* Harvey P. Dale, Dec 27 2013 *)

PROG

(PARI) Vec(1/(1+2*x-x^2+2*x^3)+O(x^40)) \\ Charles R Greathouse IV, Sep 27 2012

(MAGMA) R<x>:=PowerSeriesRing(Integers(), 40); Coefficients(R!( 1/(1+2*x-x^2+2*x^3) )); // G. C. Greubel, Jun 25 2019

(Sage) (1/(1+2*x-x^2+2*x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Jun 25 2019

(GAP) a:=[1, -2, 5];; for n in [4..40] do a[n]:=-2*a[n-1]+a[n-2]-2*a[n-3]; od; a; # G. C. Greubel, Jun 25 2019

CROSSREFS

Cf. A077938.

Sequence in context: A099485 A038990 A077938 * A143141 A117294 A148306

Adjacent sequences:  A077984 A077985 A077986 * A077988 A077989 A077990

KEYWORD

sign,easy

AUTHOR

N. J. A. Sloane, Nov 17 2002

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 November 20 20:46 EST 2019. Contains 329347 sequences. (Running on oeis4.)