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%I
%S 1,-4,-24,-32,80,384,448,-1024,-4608,-5120,11264,49152,53248,-114688,
%T -491520,-524288,1114112,4718592,4980736,-10485760,-44040192,
%U -46137344,96468992,402653184,419430400,-872415232,-3623878656,-3758096384
%N sin((2*n+5)*Pi/6)*(n+1)*2^(n+1)
%C From log((1+x)/(1-x+x^2)) at x=1/2,
%C Sum_{k>=0} 1/a(k) = log(2)
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (4,-12,16,-16).
%F G.f.: (1-8*x+4*x^2)/(1-2*x+4*x^2)^2
%o (PARI) a(n)=[1,-1,-2,-1,1,2][n%6+1]*(n+1)*2^n
%Y Cf. A002162.
%K sign
%O 0,2
%A _Jaume Oliver Lafont_, Apr 28 2010
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