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A131561 Period 3: repeat 1, 1, -1. +0
2
1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1, -1, 1, 1 (list; graph; listen)
OFFSET

0,1

FORMULA

a(n)=(1/9)*{-5*(n mod 3)+7*[(n+1) mod 3]+[(n+2) mod 3]}, with n>=0. - Paolo P. Lava (ppl(AT)spl.at), Aug 28 2007

a(n) = (4*cos((2*n - 1) * Pi/3) + 1) / 3 - Federico Acha Neckar (f0383864(AT)hotmail.com), Sep 02 2007

G.f.: (-1-x+x^2)/(x-1)/(x^2+x+1). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 14 2007

MAPLE

A131561 := proc(n) op((n mod 3)+1, [1, 1, -1]) ; end: seq(A131561(n), n=0..120) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 18 2007

CROSSREFS

Adjacent sequences: A131558 A131559 A131560 this_sequence A131562 A131563 A131564

Sequence in context: A121241 A122188 A130151 this_sequence A065357 A071935 A096809

KEYWORD

sign,easy

AUTHOR

Paul Curtz (bpcrtz(AT)free.fr), Aug 27 2007

EXTENSIONS

Edited by njas, Sep 15 2007

More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 18 2007

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Last modified May 16 23:01 EDT 2008. Contains 139884 sequences.


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