The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A084247 a(n) = -a(n-1) + 2*a(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) = A077925(n-1) + 1. a(n) = (4 - (-2)^n)/3. G.f.: (1+3*x)/((1-x)*(1+2*x)). E.g.f.: (4*exp(x) - exp(-2*x))/3. a(n) = (-1)^(n+1)*(A078008(n+1) - A078008(n)). - 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-(-2)^n)/3: n in [0..40]]; // Vincenzo Librandi, Aug 13 2011 (PARI) Vec((1+3*x)/((1-x)*(1+2*x)) + O(x^40)) \\ Michel Marcus, Feb 25 2016 (SageMath) [(4-(-2)^n)/3 for n in range(41)] # G. C. Greubel, Apr 24 2023 CROSSREFS Cf. A077925, A078008, A084246, 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 June 16 18:41 EDT 2024. Contains 373432 sequences. (Running on oeis4.)