%I #17 Jun 23 2022 09:49:26

%S 1,3,7,19,46,119,296,753,1891,4784,12052,30435,76752,193708,488664,

%T 1233061,3110965,7849501,19804697,49969640,126077463,318106522,

%U 802611677,2025068125,5109437370,12891603348,32526741151,82068086418,207065613652,522446355976,1318182069433,3325899406919

%N Expansion of (1 + 2*x)/(1 - x - 4*x^2 + x^4).

%H Harvey P. Dale, <a href="/A280756/b280756.txt">Table of n, a(n) for n = 0..1000</a>

%H R. Sachdeva and A. K. Agarwal, <a href="https://doi.org/10.1016/j.disc.2016.09.009">Combinatorics of certain restricted n-color composition functions</a>, Discrete Mathematics, 340, (2017), 361-372. See sequence C_5.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,4,0,-1).

%t CoefficientList[Series[(1+2x)/(1-x-4x^2+x^4),{x,0,40}],x] (* or *) LinearRecurrence[ {1,4,0,-1},{1,3,7,19},40] (* _Harvey P. Dale_, Jun 23 2022 *)

%K nonn,easy

%O 0,2

%A _N. J. A. Sloane_, Jan 16 2017