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%I #5 Jun 27 2013 09:57:17
%S 1,-3,-6,28,56,-288,-576,3008,6016,-31488,-62976,329728,659456,
%T -3452928,-6905856,36159488,72318976,-378667008,-757334016,3965452288,
%U 7930904576,-41526755328,-83053510656,434873827328
%N Hankel transform of A128057.
%C a(n)=2^A128054(n)*A128053(n). Hankel transform of A128058.
%F a(n)=A128055(n)*((cos(pi*n/2)-sin(pi*n/2))((F(n-1)+F(n+1))(5/6-cos(pi*n/3)/3)(1+(-1)^n)/2 +(F(n)+F(n+2))(5/6-cos(pi*(n+1)/3)/3)(1-(-1)^n)/2)).
%F Empirical g.f.: -(2*x-1)*(4*x^2-x+1) / (16*x^4+12*x^2+1). - _Colin Barker_, Jun 27 2013
%K easy,sign
%O 0,2
%A _Paul Barry_, Feb 13 2007