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Search: id:A131561
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| A131561 |
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Period 3: repeat 1, 1, -1. |
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+0
2
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| 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)
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OFFSET
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0,1
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FORMULA
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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
G.f.: (1+x-x^2)/(1-x^3) [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 24 2009]
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MAPLE
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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
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PROGRAM
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(PARI) a(n)=1-2*(n%3==2) [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 24 2009]
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CROSSREFS
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Sequence in context: A065357 A071935 A096809 this_sequence A110515 A071936 A084904
Adjacent sequences: A131558 A131559 A131560 this_sequence A131562 A131563 A131564
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KEYWORD
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sign,easy
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AUTHOR
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Paul Curtz (bpcrtz(AT)free.fr), Aug 27 2007
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Sep 15 2007
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 18 2007
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