|
| |
|
|
A131556
|
|
Period 6: repeat 1,-2,1,-1,2,-1.
|
|
6
| |
|
|
1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1, 1, -2, 1, -1, 2, -1
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (0,0,-1)
|
|
|
FORMULA
| a(n)=(1/6)*{-2*(n mod 6)+3*[(n+1) mod 6]-3*[(n+2) mod 6]+2*[(n+3) mod 6]-3*[(n+4) mod 6]+3*[(n+5) mod 6]}, with n>=0. - Paolo P. Lava (paoloplava(AT)gmail.com), Aug 28 2007
G.f.: (x-1)^2/(x+1)/(x^2-x+1). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 14 2007
a(n) = (-1)^n*A131534(n). - R. J. Mathar, Apr 02 2011
a(n)= -cos(Pi*n/3)/3 -sin(Pi*n/3)/sqrt(3) +4*(-1)^n/3. - R. J. Mathar, Oct 08 2011
|
|
|
PROG
| (PARI) a(n)=[1, -2, 1, -1, 2, -1][n%6+1] \\ Charles R Greathouse IV, Jun 02 2011
|
|
|
CROSSREFS
| Sequence in context: A100063 A057079 A132419 * A107751 A132367 A087204
Adjacent sequences: A131553 A131554 A131555 * A131557 A131558 A131559
|
|
|
KEYWORD
| sign,easy,less
|
|
|
AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Aug 27 2007
|
|
|
EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Sep 15 2007
|
| |
|
|
