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

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A084247 a(n) = -a(n-1) + 2a(n-2), a(0)=1, a(1)=2. 20
 1, 2, 0, 4, -4, 12, -20, 44, -84, 172, -340, 684, -1364, 2732, -5460, 10924, -21844, 43692, -87380, 174764, -349524, 699052, -1398100, 2796204, -5592404, 11184812, -22369620, 44739244, -89478484, 178956972, -357913940, 715827884, -1431655764, 2863311532 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Row sums of triangle in A112555. [Philippe Deléham, Sep 21 2009] LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (-1,2). FORMULA Binomial transform of A084246. a(n+1)=A077925(n)+1. a(n) = 4/3 - (-2)^n/3. G.f.: (1+3x)/((1-x)(1+2x)). E.g.f.: (4*exp(x)-exp(-2x))/3. (-1)^(n+1)*a(n) = A078008(n+1)-A078008(n). [apart from signs the second differences of A001045]. - Paul Curtz, Jun 30 2008, Feb 24 2021 a(n) = -2*a(n-1)+4 . [Philippe Deléham, Sep 15 2009] a(n+1) = 2*A151575(n). [Philippe Deléham, Sep 21 2009] a(n) = A077925(n)+3*A077925(n-1). - R. J. Mathar, Feb 24 2021 MATHEMATICA LinearRecurrence[{-1, 2}, {1, 2}, 40] (* Harvey P. Dale, Nov 05 2016 *) PROG (Magma) [4/3-(-2)^n/3: n in [0..35]]; // Vincenzo Librandi, Aug 13 2011 (PARI) Vec((1+3*x)/((1-x)*(1+2*x)) + O(x^40)) \\ Michel Marcus, Feb 25 2016 CROSSREFS Cf. A001045, A077925, A078008, A112555, A151575. Sequence in context: A195395 A296805 A336974 * A300307 A286606 A266587 Adjacent sequences: A084244 A084245 A084246 * A084248 A084249 A084250 KEYWORD easy,sign AUTHOR Paul Barry, May 23 2003 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.

Last modified December 7 19:19 EST 2022. Contains 358669 sequences. (Running on oeis4.)