%I #4 Sep 11 2017 20:04:56

%S 1,3,9,26,72,195,520,1368,3560,9184,23520,59860,151536,381840,958256,

%T 2396192,5972736,14845040,36801792,91021056,224642304,553347072,

%U 1360598016,3340024384,8186748160,20038426368,48983457024,119593531904,291657627648,710522702592

%N a(n) = (1/4)*A291732(n).

%H Clark Kimberling, <a href="/A291733/b291733.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (4, -4, 4, -8, 0, -4)

%F G.f.: -(((1 + x^2) (-1 + x + x^3))/(-1 + 2 x + 2 x^3)^2).

%F a(n) = 4*a(n-1) - 4*a(n-2) + 4*a(n-3) - 8*a(n-4) - 4*a(n-6) for n >= 7.

%t z = 60; s = x + x^3; p = (1 - 2 s)^2;

%t Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A154272 *)

%t u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A291732 *)

%t u / 4 (*A291733)

%Y Cf. A154272, A291728, A291732.

%K nonn,easy

%O 0,2

%A _Clark Kimberling_, Sep 11 2017