%I #13 Jan 02 2024 08:59:53

%S 1,0,0,0,2,2,4,8,18,34,68,136,274,546,1092,2184,4370,8738,17476,34952,

%T 69906,139810,279620,559240,1118482,2236962,4473924,8947848,17895698,

%U 35791394,71582788,143165576,286331154,572662306,1145324612,2290649224

%N a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4).

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1,2).

%F O.g.f: (-1+x+x^2+x^3)/((2*x-1)(1+x)(1+x^2)). a(n)=2^n/15+(-1)^n/3+A112030(n)/5. - _R. J. Mathar_, Jun 12 2008

%K nonn

%O 0,5

%A _Paul Curtz_, May 22 2008

%E More terms from _R. J. Mathar_, Jun 12 2008