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A084775 a(n) = sum of absolute valued coefficients of (1+1*x-4*x^2)^n. 2

%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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Last modified January 29 20:09 EST 2023. Contains 359926 sequences. (Running on oeis4.)