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A131714 Period 6: repeat [1, -2, 2, -1, 2, -2]. 2
1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..73.

Index entries for linear recurrences with constant coefficients, signature (0,0,-1).

FORMULA

a(n) = (1/6)*{-3*(n mod 6)+4*[(n+1) mod 6]-3*[(n+2) mod 6]+3*[(n+3) mod 6]-4*[(n+4) mod 6]+3*[(n+5) mod 6]}. - Paolo P. Lava, Oct 02 2007

G.f.: (1-2*x+2*x^2)/(x+1)/(x^2-x+1). - R. J. Mathar, Nov 14 2007

From Wesley Ivan Hurt, Jun 19 2016: (Start)

a(n) + a(n-3) = 0 for n>2.

a(n) = (5*cos(n*Pi)-2*cos(n*Pi/3))/3. (End)

MAPLE

A131714:=n->[1, -2, 2, -1, 2, -2][(n mod 6)+1]: seq(A131714(n), n=0..100); # Wesley Ivan Hurt, Jun 19 2016

MATHEMATICA

PadRight[{}, 200, {1, -2, 2, -1, 2, -2}] (* Wesley Ivan Hurt, Jun 19 2016 *)

PROG

(MAGMA) &cat[[1, -2, 2, -1, 2, -2]^^20]; // Wesley Ivan Hurt, Jun 19 2016

CROSSREFS

Cf. A130196, A131556.

Sequence in context: A243759 A098398 A306211 * A130196 A230866 A158209

Adjacent sequences:  A131711 A131712 A131713 * A131715 A131716 A131717

KEYWORD

sign,easy

AUTHOR

Paul Curtz, Sep 14 2007

STATUS

approved

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Last modified July 11 21:30 EDT 2020. Contains 335652 sequences. (Running on oeis4.)