%I A131720
%S A131720 0,1,1,1,1,0,0,1,1,1,1,0,0,1,1,1,1,0,0,1,1,1,1,0,0,1,1,1,1,0,0,1,1,1,1,
%T A131720 0,0,1,1,1,1,0,0,1,1,1,1,0
%V A131720 0,1,-1,1,-1,0,0,1,-1,1,-1,0,0,1,-1,1,-1,0,0,1,-1,1,-1,0,0,1,-1,1,-1,0,
               0,1,-1,1,-1,0,0,
%W A131720 1,-1,1,-1,0,0,1,-1,1,-1,0
%N A131720 Period 6: repeat 0,1,-1,1,-1,0.
%F A131720 a(n)=(1/6)*{-[(n+1) mod 6]+2*[(n+2) mod 6]-2*[(n+3) mod 6]+2*[(n+4) mod 
               6]-[(n+5) mod 6]}, with n>=0 - Paolo P. Lava (ppl(AT)spl.at), Oct 
               02 2007
%F A131720 a(n) = 1/6*cos(1/3*Pi*n)+1/6*3^(1/2)*sin(1/3*Pi*n)+1/2*cos(2/3*Pi*n)+1/
               6*3^(1/2)*sin(2/3*Pi*n)+2/3*(-1)^(1+n). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Nov 15 2007
%F A131720 G.f.:(x*(x^2+1))/((x+1)*(x^2-x+1)*(x^2+x+1)) [From Maksym Voznyy (voznyy(AT)mail.ru), 
               Aug 11 2009]
%Y A131720 Sequence in context: A099859 A102460 A080908 this_sequence A131719 A100656 
               A053867
%Y A131720 Adjacent sequences: A131717 A131718 A131719 this_sequence A131721 A131722 
               A131723
%K A131720 sign
%O A131720 0,1
%A A131720 Paul Curtz (bpcrtz(AT)free.fr), Sep 15 2007