%I
%S 1,6,34,184,956,4776,22986,118304,624634,3281346,17687330,92606914,
%T 470392898,2348031430,11932314170,62345998488,326780375778,
%U 1691296908076,8780141027670,45168987187058,230213109996786
%N a(n) = sum of absolute valued coefficients of (1+1*x-4*x^2)^n.
%o (PARI) for(n=0,40,S=sum(k=0,2*n,abs(polcoeff((1+1*x-4*x^2)^n,k,x))); print1(S","))
%K nonn
%O 0,2
%A _Paul D. Hanna_, Jun 14 2003
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